8.17.2

8.18.1

SENDMAILTM

INSTALLATION AND OPERATION GUIDE

Eric Allman

Claus Assmann

Gregory Neil Shapiro

Proofpoint, Inc.

For Sendmail Version 8.18

SendmailTM implements a general purpose internetwork mail routing facility under the UNIX® oper-

ating system. It is not tied to any one transport protocol — its function may be likened to a crossbar switch,

relaying messages from one domain into another. In the process, it can do a limited amount of message

header editing to put the message into a format that is appropriate for the receiving domain. All of this is

done under the control of a conguration le.

Due to the requirements of exibility for sendmail, the conguration le can seem somewhat unap-

proachable. However, there are only a few basic congurations for most sites, for which standard congu-

ration les have been supplied. Most other congurations can be built by adjusting an existing congura-

tion le incrementally.

Sendmail is based on RFC 821 (Simple Mail Transport Protocol), RFC 822 (Internet Mail Headers

Format), RFC 974 (MX routing), RFC 1123 (Internet Host Requirements), RFC 1413 (Identication

server), RFC 1652 (SMTP 8BITMIME Extension), RFC 1869 (SMTP Service Extensions), RFC 1870

(SMTP SIZE Extension), RFC 1891 (SMTP Delivery Status Notications), RFC 1892 (Multipart/Report),

RFC 1893 (Enhanced Mail System Status Codes), RFC 1894 (Delivery Status Notications), RFC 1985

(SMTP Service Extension for Remote Message Queue Starting), RFC 2033 (Local Message Transmission

Protocol), RFC 2034 (SMTP Service Extension for Returning Enhanced Error Codes), RFC 2045 (MIME),

RFC 2476 (Message Submission), RFC 2487 (SMTP Service Extension for Secure SMTP over TLS), RFC

2554 (SMTP Service Extension for Authentication), RFC 2821 (Simple Mail Transfer Protocol), RFC 2822

(Internet Message Format), RFC 2852 (Deliver By SMTP Service Extension), RFC 2920 (SMTP Service

Extension for Command Pipelining), and RFC 7505 (A "Null MX" No Service Resource Record for

Domains That Accept No Mail). However, since sendmail is designed to work in a wider world, in many

cases it can be congured to exceed these protocols. These cases are described herein.

Although sendmail is intended to run without the need for monitoring, it has a number of features

that may be used to monitor or adjust the operation under unusual circumstances. These features are

described.

Section one describes how to do a basic sendmail installation. Section two explains the day-to-day

information you should know to maintain your mail system. If you have a relatively normal site, these two

sections should contain sufcient information for you to install sendmail and keep it happy. Section three

has information regarding the command line arguments. Section four describes some parameters that may

DISCLAIMER: This documentation is under modication.

Sendmail is a trademark of Proofpoint, Inc. US Patent Numbers 6865671, 6986037.

Sendmail Installation and Operation Guide

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Sendmail Installation and Operation Guide

be safely tweaked. Sectionve contains the nitty-gritty information about the conguration le. This sec-

tion is for masochists and people who must write their own conguration le. Section six describes cong-

uration that can be done at compile time. The appendixes give a brief but detailed explanation of a number

of features not described in the rest of the paper.

Sendmail Installation and Operation Guide

SMM:08-3

TABLE OF CONTENTS

1. BASIC INSTALLATION ...............................................................................................................

7

1.1. Compiling Sendmail ..............................................................................................................

7

1.1.1. Tweaking the Build Invocation .....................................................................................

7

1.1.2. Creating a Site Conguration File ................................................................................

7

1.1.3. Tweaking the Makele .................................................................................................

8

1.1.4. Compilation and installation ........................................................................................

8

1.2. Conguration Files ................................................................................................................

8

1.3. Details of Installation Files ...................................................................................................

10

1.3.1. /usr/sbin/sendmail .........................................................................................................

10

1.3.2. /etc/mail/sendmail.cf ....................................................................................................

10

1.3.3. /etc/mail/submit.cf ........................................................................................................

10

1.3.4. /usr/bin/newaliases .......................................................................................................

10

1.3.5. /usr/bin/hoststat ............................................................................................................

10

1.3.6. /usr/bin/purgestat ..........................................................................................................

11

1.3.7. /var/spool/mqueue ........................................................................................................

11

1.3.8. /var/spool/clientmqueue ...............................................................................................

11

1.3.9. /var/spool/mqueue/.hoststat ..........................................................................................

11

1.3.10. /etc/mail/aliases* ........................................................................................................

11

1.3.11. /etc/rc or /etc/init.d/sendmail ......................................................................................

12

1.3.12. /etc/mail/helple .........................................................................................................

12

1.3.13. /etc/mail/statistics .......................................................................................................

12

1.3.14. /usr/bin/mailq .............................................................................................................

12

1.3.15. sendmail.pid ...............................................................................................................

12

1.3.16. Map Files ....................................................................................................................

14

2. NORMAL OPERATIONS .............................................................................................................

14

2.1. The System Log ....................................................................................................................

14

2.1.1. Format ..........................................................................................................................

14

2.1.2. Levels ...........................................................................................................................

15

2.2. Dumping State .......................................................................................................................

15

2.3. The Mail Queues ...................................................................................................................

16

2.3.1. Queue Groups and Queue Directories ..........................................................................

16

2.3.2. Queue Runs ..................................................................................................................

16

2.3.3. Manual Intervention .....................................................................................................

17

2.3.4. Printing the queue .........................................................................................................

17

2.3.5. Forcing the queue .........................................................................................................

17

2.3.6. Quarantined Queue Items .............................................................................................

18

2.4. Disk Based Connection Information .....................................................................................

18

2.5. The Service Switch ................................................................................................................

19

2.6. The Alias Database ................................................................................................................

20

2.6.1. Rebuilding the alias database .......................................................................................

21

2.6.2. Potential problems ........................................................................................................

21

2.6.3. List owners ...................................................................................................................

21

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Sendmail Installation and Operation Guide

2.7. User Information Database ....................................................................................................

22

2.8. Per-User Forwarding (.forward Files) ...................................................................................

22

2.9. Special Header Lines .............................................................................................................

22

2.9.1. Errors-To: .....................................................................................................................

22

2.9.2. Apparently-To: .............................................................................................................

22

2.9.3. Precedence ....................................................................................................................

23

2.10. IDENT Protocol Support .....................................................................................................

23

3. ARGUMENTS ...............................................................................................................................

23

3.1. Queue Interval .......................................................................................................................

23

3.2. Daemon Mode .......................................................................................................................

24

3.3. Forcing the Queue .................................................................................................................

24

3.4. Debugging .............................................................................................................................

24

3.5. Changing the Values of Options ............................................................................................

25

3.6. Trying a Different Conguration File ...................................................................................

25

3.7. Logging Trafc ......................................................................................................................

26

3.8. Testing Conguration Files ...................................................................................................

26

3.9. Persistent Host Status Information ........................................................................................

27

4. TUNING .........................................................................................................................................

27

4.1. Timeouts ................................................................................................................................

27

4.1.1. Queue interval ..............................................................................................................

28

4.1.2. Read timeouts ...............................................................................................................

28

4.1.3. Message timeouts .........................................................................................................

29

4.2. Forking During Queue Runs .................................................................................................

30

4.3. Queue Priorities .....................................................................................................................

30

4.4. Load Limiting ........................................................................................................................

31

4.5. Resource Limits .....................................................................................................................

31

4.6. Measures against Denial of Service Attacks .........................................................................

31

4.7. Delivery Mode .......................................................................................................................

32

4.8. Log Level ...............................................................................................................................

32

4.9. File Modes .............................................................................................................................

33

4.9.1. To suid or not to suid? .................................................................................................

33

4.9.2. Turning off security checks ..........................................................................................

33

4.10. Connection Caching ............................................................................................................

36

4.11. Name Server Access ............................................................................................................

36

4.12. Moving the Per-User Forward Files ....................................................................................

37

4.13. Free Space ...........................................................................................................................

37

4.14. Maximum Message Size .....................................................................................................

38

4.15. Privacy Flags .......................................................................................................................

38

4.16. Send to Me Too ...................................................................................................................

38

5. THE WHOLE SCOOP ON THE CONFIGURATION FILE ........................................................

38

5.1. R and S — Rewriting Rules ..................................................................................................

38

5.1.1. The left hand side .........................................................................................................

39

5.1.2. The right hand side .......................................................................................................

39

5.1.3. Semantics of rewriting rule sets ...................................................................................

41

Sendmail Installation and Operation Guide

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5.1.4. Ruleset hooks ...............................................................................................................

42

5.1.4.1. check_relay ..........................................................................................................

42

5.1.4.2. check_mail ..........................................................................................................

42

5.1.4.3. check_rcpt ...........................................................................................................

42

5.1.4.4. check_data ...........................................................................................................

42

5.1.4.5. check_other .........................................................................................................

42

5.1.4.6. check_compat ......................................................................................................

43

5.1.4.7. check_eoh ............................................................................................................

43

5.1.4.8. check_eom ...........................................................................................................

43

5.1.4.9. check_etrn ...........................................................................................................

44

5.1.4.10. check_expn ........................................................................................................

44

5.1.4.11. check_vrfy .........................................................................................................

44

5.1.4.12. clt_features ........................................................................................................

44

5.1.4.13. trust_auth ...........................................................................................................

44

5.1.4.14. tls_client ............................................................................................................

44

5.1.4.15. tls_server ...........................................................................................................

44

5.1.4.16. tls_rcpt ...............................................................................................................

44

5.1.4.17. srv_features .......................................................................................................

45

5.1.4.18. try_tls .................................................................................................................

46

5.1.4.19. tls_srv_features and tls_clt_features .................................................................

46

5.1.4.20. authinfo ..............................................................................................................

47

5.1.4.21. queuegroup ........................................................................................................

48

5.1.4.22. greet_pause ........................................................................................................

48

5.1.5. IPC mailers ...................................................................................................................

48

5.2. D — Dene Macro ................................................................................................................

49

5.3. C and F — Dene Classes .....................................................................................................

56

5.4. E — Set or Propagate Environment Variables ......................................................................

57

5.5. M — Dene Mailer ...............................................................................................................

58

5.6. H — Dene Header ...............................................................................................................

62

5.7. O — Set Option .....................................................................................................................

63

5.8. P — Precedence Denitions ..................................................................................................

83

5.9. V — Conguration Version Level .........................................................................................

83

5.10. K — Key File Declaration ...................................................................................................

84

5.11. Q — Queue Group Declaration ...........................................................................................

92

5.12. X — Mail Filter (Milter) Denitions ..................................................................................

93

5.13. The User Database ..............................................................................................................

94

5.13.1. Structure of the user database .....................................................................................

94

5.13.2. User database semantics .............................................................................................

95

5.13.3. Creating the database23 ...............................................................................................

95

6. OTHER CONFIGURATION .........................................................................................................

96

6.1. Parameters in devtools/OS/$oscf ...........................................................................................

96

6.1.1. For Future Releases ......................................................................................................

97

6.2. Parameters in sendmail/conf.h ..............................................................................................

97

6.3. Conguration in sendmail/conf.c ..........................................................................................

100

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Sendmail Installation and Operation Guide

6.3.1. Built-in Header Semantics ...........................................................................................

100

6.3.2. Restricting Use of Email ..............................................................................................

101

6.3.3. New Database Map Classes .........................................................................................

102

6.3.4. Queueing Function .......................................................................................................

102

6.3.5. Refusing Incoming SMTP Connections .......................................................................

103

6.3.6. Load Average Computation ..........................................................................................

103

6.4. Conguration in sendmail/daemon.c .....................................................................................

103

6.5. LDAP .....................................................................................................................................

104

6.5.1. LDAP Recursion ..........................................................................................................

104

6.5.1.1. Example ...............................................................................................................

104

6.6. STARTTLS ............................................................................................................................

105

6.6.1. Certicates for STARTTLS ..........................................................................................

105

6.6.2. PRNG for STARTTLS .................................................................................................

105

6.7. Encoding of STARTTLS and AUTH related Macros ............................................................

106

6.8. DANE ....................................................................................................................................

106

6.9. EAI ........................................................................................................................................

107

6.10. MTA-STS ............................................................................................................................

107

7. ACKNOWLEDGEMENTS ............................................................................................................

107

Appendix A. COMMAND LINE FLAGS .........................................................................................

109

Appendix B. QUEUE FILE FORMATS ............................................................................................

112

Appendix C. SUMMARY OF SUPPORT FILES ..............................................................................

115

Sendmail Installation and Operation Guide

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1. BASIC INSTALLATION

There are two basic steps to installing sendmail. First, you have to compile and install the binary.

If sendmail has already been ported to your operating system that should be simple. Second, you must

build a run-time conguration le. This is a le that sendmail reads when it starts up that describes the

mailers it knows about, how to parse addresses, how to rewrite the message header, and the settings of

various options. Although the conguration le can be quite complex, a conguration can usually be

built using an M4-based conguration language. Assuming you have the standard sendmail distribu-

tion, see cf/README for further information.

The remainder of this section will describe the installation of sendmail assuming you can use one

of the existing congurations and that the standard installation parameters are acceptable. All path-

names and examples are given from the root of the sendmail subtree, normally /usr/src/usr.sbin/send-

mail on 4.4BSD-based systems.

Continue with the next section if you need/want to compile sendmail yourself. If you have a run-

ning binary already on your system, you should probably skip to section 1.2.

1.1. Compiling Sendmail

All sendmail source is in the sendmail subdirectory. To compile sendmail, “cd” into the send-

mail directory and type

./Build

This will leave the binary in an appropriately named subdirectory, e.g., obj.BSD-OS.2.1.i386. It

works for multiple object versions compiled out of the same directory.

1.1.1. Tweaking the Build Invocation

You can give parameters on the Build command. In most cases these are only used when

the obj.* directory is rst created. To restart from scratch, use -c. These commands include:

L libdirs

A list of directories to search for libraries.

I incdirs

A list of directories to search for include les.

E envar=value

Set an environment variable to an indicated value before compiling.

c

Create a new obj.* tree before running.

f sitecong

Read the indicated site conguration le. If this parameter is not specied, Build

includes

all

of

the

les

$BUILDTOOLS/Site/site.$oscf.m4

and

$BUILD-

TOOLS/Site/site.cong.m4, where $BUILDTOOLS is normally ../devtools and $oscf is

the same name as used on the obj.* directory. See below for a description of the site

conguration le.

S

Skip auto-conguration. Build will avoid auto-detecting libraries if this is set. All

libraries and map denitions must be specied in the site conguration le.

Most other parameters are passed to the

make

program; for details see

$BUILD-

TOOLS/README.

1.1.2. Creating a Site Conguration File

See sendmail/README for various compilation ags that can be set, and dev-

tools/README for details how to set them.

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Sendmail Installation and Operation Guide

1.1.3. Tweaking the Makele

Sendmail supports two different formats for the local (on disk) version of databases,

notably the aliases database. At least one of these should be dened if at all possible.

CDB

Constant DataBase (tinycdb).

NDBM

The ‘‘new DBM’’ format, available on nearly all systems around today. This

was the preferred format prior to 4.4BSD. It allows such complex things as

multiple databases and closing a currently open database.

NEWDB

The Berkeley DB package. If you have this, use it. It allows long records,

multiple open databases, real in-memory caching, and so forth. You can

dene this in conjunction with NDBM; if you do, old alias databases are read,

but when a new database is created it will be in NEWDB format. As a nasty

hack, if you have NEWDB, NDBM, and NIS dened, and if the alias le

name includes the substring “/yp/”, sendmail will create both new and old ver-

sions of the alias le during a newalias command. This is required because

the Sun NIS/YP system reads the DBM version of the alias le. It’s ugly as

sin, but it works.

If neither of these are dened, sendmail reads the alias le into memory on every invocation.

This can be slow and should be avoided. There are also several methods for remote database

access:

LDAP

Lightweight Directory Access Protocol.

NIS

Sun’s Network Information Services (formerly YP).

NISPLUS

Sun’s NIS+ services.

NETINFO

NeXT’s NetInfo service.

HESIOD

Hesiod service (from Athena).

Other compilation ags are set in conf.h and should be predened for you unless you are porting

to a new environment. For more options see sendmail/README.

1.1.4. Compilation and installation

After making the local system conguration described above, You should be able to com-

pile and install the system. The script “Build” is the best approach on most systems:

./Build

This will use uname(1) to create a custom Makele for your environment.

If you are installing in the standard places, you should be able to install using

./Build install

This should install the binary in /usr/sbin and create links from /usr/bin/newaliases and

/usr/bin/mailq to /usr/sbin/sendmail. On most systems it will also format and install man pages.

Notice: as of version 8.12 sendmail will no longer be installed set-user-ID root by default. If

you really want to use the old method, you can specify it as target:

./Build install-set-user-id

1.2. Conguration Files

Sendmail cannot operate without a conguration le. The conguration denes the mail

delivery mechanisms understood at this site, how to access them, how to forward email to remote

mail systems, and a number of tuning parameters. This conguration le is detailed in the later por-

tion of this document.

Sendmail Installation and Operation Guide

SMM:08-9

The sendmail conguration can be daunting at rst. The world is complex, and the mail con-

guration reects that. The distribution includes an m4-based conguration package that hides a lot

of the complexity. See cf/README for details.

Our conguration les are processed by m4 to facilitate local customization; the directory cf

of the sendmail distribution directory contains the source les. This directory contains several sub-

directories:

cf

Both site-dependent and site-independent descriptions of hosts. These can be lit-

eral host names (e.g., “ucbvax.mc”) when the hosts are gateways or more general

descriptions (such as “generic-solaris2.mc” as a general description of an SMTP-

connected host running Solaris 2.x. Files ending .mc (‘‘M4 Conguration’’) are

the input descriptions; the output is in the corresponding .cfle. The general

structure of these les is described below.

domain

Site-dependent subdomain descriptions. These are tied to the way your organiza-

tion wants to do addressing. For example, domain/CS.Berkeley.EDU.m4 is our

description for hosts in the CS.Berkeley.EDU subdomain. These are referenced

using the DOMAIN m4 macro in the .mcle.

feature

Denitions of specic features that some particular host in your site might want.

These are referenced using the FEATURE m4 macro. An example feature is

use_cw_le (which tells sendmail to read an /etc/mail/local-host-names le on

startup to nd the set of local names).

hack

Local hacks, referenced using the HACK m4 macro. Try to avoid these. The

point of having them here is to make it clear that they smell.

m4

Site-independent m4(1) include les that have information common to all congu-

ration les. This can be thought of as a “#include” directory.

mailer

Denitions of mailers, referenced using the MAILER m4 macro. The mailer types

that are known in this distribution are fax, local, smtp, uucp, and usenet. For

example, to include support for the UUCP-based mailers, use “MAILER(uucp)”.

ostype

Denitions describing various operating system environments (such as the loca-

tion of support les). These are referenced using the OSTYPE m4 macro.

sh

Shellles used by the m4 build process. You shouldn’t hav e to mess with these.

sitecong

Local UUCP connectivity information. This directory has been supplanted by the

mailertable feature; any new congurations should use that feature to do UUCP

(and other) routing. The use of this directory is deprecated.

If you are in a new domain (e.g., a company), you will probably want to create a cf/domain

le for your domain. This consists primarily of relay denitions and features you want enabled site-

wide: for example, Berkeley’s domain denition denes relays for BitNET and UUCP. These are

specic to Berkeley, and should be fully-qualied internet-style domain names. Please check to

make certain they are reasonable for your domain.

Subdomains at Berkeley are also represented in the cf/domain directory. For example, the

domain CS.Berkeley.EDU is the Computer Science subdomain, EECS.Berkeley.EDU is the Electri-

cal Engineering and Computer Sciences subdomain, and S2K.Berkeley.EDU is the Sequoia 2000

subdomain. You will probably have to add an entry to this directory to be appropriate for your

domain.

You will have to use or create .mcles in the cf/cf subdirectory for your hosts. This is

detailed in the cf/README le.

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Sendmail Installation and Operation Guide

1.3. Details of Installation Files

This subsection describes the les that comprise the sendmail installation.

1.3.1. /usr/sbin/sendmail

The binary for sendmail is located in /usr/sbin1. It should be set-group-ID smmsp as

described in sendmail/SECURITY. For security reasons, /, /usr, and /usr/sbin should be owned

by root, mode 07552.

1.3.2. /etc/mail/sendmail.cf

This is the main conguration le for sendmail3. This is one of the two non-library le

names compiled into sendmail4, the other is /etc/mail/submit.cf.

The conguration le is normally created using the distribution les described above. If

you have a particularly unusual system conguration you may need to create a special version.

The format of this le is detailed in later sections of this document.

1.3.3. /etc/mail/submit.cf

This is the conguration le for sendmail when it is used for initial mail submission, in

which case it is also called ‘‘Mail Submission Program’’ (MSP) in contrast to ‘‘Mail Transfer

Agent’’ (MTA). Starting with version 8.12, sendmail uses one of two different conguration

les based on its operation mode (or the newA option). For initial mail submission, i.e., if one

of the optionsbm (default),bs, ort is specied, submit.cf is used (if available), for other

operations sendmail.cf is used. Details can be found in sendmail/SECURITY. submit.cf is

shipped with sendmail (in cf/cf/) and is installed by default. If changes to the conguration need

to be made, start with cf/cf/submit.mc and follow the instruction in cf/README.

1.3.4. /usr/bin/newaliases

The newaliases command should just be a link to sendmail:

rm f /usr/bin/newaliases

ln s /usr/sbin/sendmail /usr/bin/newaliases

This can be installed in whatever search path you prefer for your system.

1.3.5. /usr/bin/hoststat

The hoststat command should just be a link to sendmail, in a fashion similar to

newaliases. This command lists the status of the last mail transaction with all remote hosts.

Thevag will prevent the status display from being truncated. It functions only when the

HostStatusDirectory option is set.

1This is usually /usr/sbin on 4.4BSD and newer systems; many systems install it in /usr/lib. I understand it is in /usr/ucblib on

System V Release 4.

2Some vendors ship them owned by bin; this creates a security hole that is not actually related to sendmail. Other important di-

rectories that should have restrictive ownerships and permissions are /bin, /usr/bin, /etc, /etc/mail, /usr/etc, /lib, and /usr/lib.

3Actually, the pathname varies depending on the operating system; /etc/mail is the preferred directory. Some older systems in-

stall it in /usr/lib/sendmail.cf, and I’ve also seen it in /usr/ucblib. If you want to move this le, add -D_PATH_SENDMAIL-

CF=\"/le/name\" to the ags passed to the C compiler. Moving this le is not recommended: other programs and scripts know of this

location.

4The system libraries can reference other les; in particular, system library subroutines that sendmail calls probably reference

/etc/passwd and /etc/resolv.conf.

Sendmail Installation and Operation Guide

SMM:08-11

1.3.6. /usr/bin/purgestat

This command is also a link to sendmail. Itushes expired (Timeout.hoststatus) informa-

tion that is stored in the HostStatusDirectory tree.

1.3.7. /var/spool/mqueue

The directory /var/spool/mqueue should be created to hold the mail queue. This directory

should be mode 0700 and owned by root.

The actual path of this directory is dened by the QueueDirectory option of the send-

mail.cfle. To use multiple queues, supply a value ending with an asterisk. For example,

/var/spool/mqueue/qd* will use all of the directories or symbolic links to directories beginning

with ‘qd’ in /var/spool/mqueue as queue directories. Do not change the queue directory struc-

ture while sendmail is running.

If these directories have subdirectories or symbolic links to directories named ‘qf’, ‘df’,

and ‘xf’, then these will be used for the different queue le types. That is, the data les are

stored in the ‘df’ subdirectory, the transcript les are stored in the ‘xf’ subdirectory, and all oth-

ers are stored in the ‘qf’ subdirectory.

If shared memory support is compiled in, sendmail stores the available diskspace in a

shared memory segment to make the values readily available to all children without incurring

system overhead. In this case, only the daemon updates the data; i.e., the sendmail daemon cre-

ates the shared memory segment and deletes it if it is terminated. To use this, sendmail must

have been compiled with support for shared memory (-DSM_CONF_SHM) and the option

SharedMemoryKey must be set. Notice: do not use the same key for sendmail invocations

with different queue directories or different queue group declarations. Access to shared memory

is not controlled by locks, i.e., there is a race condition when data in the shared memory is

updated. However, since operation of sendmail does not rely on the data in the shared memory,

this does not negatively inuence the behavior.

1.3.8. /var/spool/clientmqueue

The directory /var/spool/clientmqueue should be created to hold the mail queue. This

directory should be mode 0770 and owned by user smmsp, group smmsp.

The actual path of this directory is dened by the QueueDirectory option of the submit.cf

le.

1.3.9. /var/spool/mqueue/.hoststat

This is a typical value for the HostStatusDirectory option, containing one le per host

that this sendmail has chatted with recently. It is normally a subdirectory of mqueue.

1.3.10. /etc/mail/aliases*

The system aliases are held in “/etc/mail/aliases”. A sample is given in “sendmail/aliases”

which includes some aliases which must be dened:

cp sendmail/aliases /etc/mail/aliases

edit /etc/mail/aliases

You should extend this le with any aliases that are apropos to your system.

Normally sendmail looks at a database version of the les, stored either in

“/etc/mail/aliases.dir” and “/etc/mail/aliases.pag” or “/etc/mail/aliases.db” depending on which

database package you are using. The actual path of this le is dened in the AliasFile option of

the sendmail.cfle.

SMM:08-12

Sendmail Installation and Operation Guide

The permissions of the alias le and the database versions should be 0640 to prevent local

denial of service attacks as explained in the top level README in the sendmail distribution. If

the permissions 0640 are used, be sure that only trusted users belong to the group assigned to

those les. Otherwise, les should not even be group readable.

1.3.11. /etc/rc or /etc/init.d/sendmail

It will be necessary to start up the sendmail daemon when your system reboots. This dae-

mon performs two functions: it listens on the SMTP socket for connections (to receive mail

from a remote system) and it processes the queue periodically to insure that mail gets delivered

when hosts come up.

If necessary, add the following lines to “/etc/rc” (or “/etc/rc.local” as appropriate) in the

area where it is starting up the daemons on a BSD-base system, or on a System-V-based system

in one of the startup les, typically “/etc/init.d/sendmail”:

if [ f /usr/sbin/sendmail a f /etc/mail/sendmail.cf ]; then

(cd /var/spool/mqueue; rm f xf*)

/usr/sbin/sendmail bd q30m &

echo n ’ sendmail’ >/dev/console

The “cd” and “rm” commands insure that all transcript les have been removed; extraneous

transcript les may be left around if the system goes down in the middle of processing a mes-

sage. The line that actually invokes sendmail has twoags: “bd” causes it to listen on the

SMTP port, and “q30m” causes it to run the queue every half hour.

Some people use a more complex startup script, removing zero length qf/hf/Qf les and df

les for which there is no qf/hf/Qf le. Note this is not advisable. For example, see Figure 1 for

an example of a complex script which does this clean up.

1.3.12. /etc/mail/helple

This is the help le used by the SMTP HELP command. It should be copied from “send-

mail/helple”:

cp sendmail/helple /etc/mail/helple

The actual path of this le is dened in the HelpFile option of the sendmail.cfle.

1.3.13. /etc/mail/statistics

If you wish to collect statistics about your mail trafc, you should create the le

“/etc/mail/statistics”:

cp /dev/null /etc/mail/statistics

chmod 0600 /etc/mail/statistics

This le does not grow. It is printed with the program “mailstats/mailstats.c.” The actual path

of this le is dened in the S option of the sendmail.cfle.

1.3.14. /usr/bin/mailq

If sendmail is invoked as “mailq,” it will simulate thebpag (i.e., sendmail will print

the contents of the mail queue; see below). This should be a link to /usr/sbin/sendmail.

1.3.15. sendmail.pid

sendmail stores its current pid in the le specied by the PidFile option (default is

_PATH_SENDMAILPID). sendmail uses TempFileMode (which defaults to 0600) as the per-

missions of that le to prevent local denial of service attacks as explained in the top level

Sendmail Installation and Operation Guide

SMM:08-13

#!/bin/sh

# remove zero length qf/hf/Qf les

for qfle in qf* hf* Qf*

do

if [ r $qfle ]

then

if [ ! s $qfle ]

then

echo n " <zero: $qfle>" > /dev/console

rm f $qfle

done

# rename tf les to be qf if the qf does not exist

for tfle in tf*

do

qfle=‘echo $tfle | sed ’s/t/q/’‘

if [ r $tfle a ! f $qfle ]

then

echo n " <recovering: $tfle>" > /dev/console

mv $tfle $qfle

else

if [ f $tfle ]

then

echo n " <extra: $tfle>" > /dev/console

rm f $tfle

done

# remove dfles with no corresponding qf/hf/Qf les

for dfle in df*

do

qfle=‘echo $dfle | sed ’s/d/q/’‘

hfle=‘echo $dfle | sed ’s/d/h/’‘

Qfle=‘echo $dfle | sed ’s/d/Q/’‘

if [ r $dfle a ! f $qfle a ! f $hfle a ! f $Qfle ]

then

echo n " <incomplete: $dfle>" > /dev/console

mv $dfle ‘echo $dfle | sed ’s/d/D/’‘

done

# announce les that have been saved during disaster recovery

for xfle in [A-Z]f*

do

if [ f $xfle ]

then

echo n " <panic: $xfle>" > /dev/console

done

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Sendmail Installation and Operation Guide

Figure 1 — A complex startup script

README in the sendmail distribution. If the le already exists, then it might be necessary to

change the permissions accordingly, e.g.,

chmod 0600 /var/run/sendmail.pid

Note that as of version 8.13, this le is unlinked when sendmail exits. As a result of this

change, a script such as the following, which may have worked prior to 8.13, will no longer

work:

# stop & start sendmail

PIDFILE=/var/run/sendmail.pid

kill ‘head -1 $PIDFILE‘

‘tail -1 $PIDFILE‘

because it assumes that the pidle will still exist even after killing the process to which it refers.

Below is a script which will work correctly on both newer and older versions:

# stop & start sendmail

PIDFILE=/var/run/sendmail.pid

pid=‘head -1 $PIDFILE‘

cmd=‘tail -1 $PIDFILE‘

kill $pid

$cmd

This is just an example script, it does not perform any error checks, e.g., whether the pidle

exists at all.

1.3.16. Map Files

To prevent local denial of service attacks as explained in the top level README in the

sendmail distribution, the permissions of map les created by makemap should be 0640. The

use of 0640 implies that only trusted users belong to the group assigned to those les. If those

les already exist, then it might be necessary to change the permissions accordingly, e.g.,

cd /etc/mail

chmod 0640 *.db *.pag *.dir

2. NORMAL OPERATIONS

2.1. The System Log

The system log is supported by the syslogd (8) program. All messages from sendmail are

logged under the LOG_MAIL facility5.

2.1.1. Format

Each line in the system log consists of a timestamp, the name of the machine that gener-

ated it (for logging from several machines over the local area network), the word “sendmail:”,

and a message6. Most messages are a sequence of name=value pairs.

5Except on Ultrix, which does not support facilities in the syslog.

6This format may vary slightly if your vendor has changed the syntax.

Sendmail Installation and Operation Guide

SMM:08-15

The two most common lines are logged when a message is processed. The rst logs the

receipt of a message; there will be exactly one of these per message. Some elds may be omit-

ted if they do not contain interesting information. Fields are:

from

The envelope sender address.

size

The size of the message in bytes.

class

The class (i.e., numeric precedence) of the message.

pri

The initial message priority (used for queue sorting).

nrcpts

The number of envelope recipients for this message (after aliasing and for-

warding).

msgid

The message id of the message (from the header).

bodytype

The message body type (7BIT or 8BITMIME), as determined from the

envelope.

proto

The protocol used to receive this message (e.g., ESMTP or UUCP)

daemon

The daemon name from the DaemonPortOptions setting.

relay

The machine from which it was received.

There is also one line logged per delivery attempt (so there can be several per message if deliv-

ery is deferred or there are multiple recipients). Fields are:

to

A comma-separated list of the recipients to this mailer.

ctladdr

The ‘‘controlling user’’, that is, the name of the user whose credentials we use

for delivery.

delay

The total delay between the time this message was received and the current

delivery attempt.

xdelay

The amount of time needed in this delivery attempt (normally indicative of the

speed of the connection).

mailer

The name of the mailer used to deliver to this recipient.

relay

The name of the host that actually accepted (or rejected) this recipient.

dsn

The enhanced error code (RFC 2034) if available.

stat

The delivery status.

Not all elds are present in all messages; for example, the relay is usually not listed for local

deliveries.

2.1.2. Levels

If you have syslogd (8) or an equivalent installed, you will be able to do logging. There is

a large amount of information that can be logged. The log is arranged as a succession of levels.

At the lowest level only extremely strange situations are logged. At the highest level, even the

most mundane and uninteresting events are recorded for posterity. As a convention, log levels

under ten are considered generally “useful;” log levels above 64 are reserved for debugging pur-

poses. Levels from 1164 are reserved for verbose information that some sites might want.

A complete description of the log levels is given in section ‘‘Log Level’’.

2.2. Dumping State

You can ask sendmail to log a dump of the open les and the connection cache by sending it a

SIGUSR1 signal. The results are logged at LOG_DEBUG priority.

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Sendmail Installation and Operation Guide

2.3. The Mail Queues

Mail messages may either be delivered immediately or be held for later delivery. Held mes-

sages are placed into a holding directory called a mail queue.

A mail message may be queued for these reasons:

• If a mail message is temporarily undeliverable, it is queued and delivery is attempted later. If the

message is addressed to multiple recipients, it is queued only for those recipients to whom deliv-

ery is not immediately possible.

• If the SuperSafe option is set to true, all mail messages are queued while delivery is attempted.

• If the DeliveryMode option is set to queue-only or defer, all mail is queued, and no immediate

delivery is attempted.

• If the load average becomes higher than the value of the QueueLA option and the QueueFactor

(q) option divided by the difference in the current load average and the QueueLA option plus

one is less than the priority of the message, messages are queued rather than immediately deliv-

ered.

• One or more addresses are marked as expensive and delivery is postponed until the next queue

run or one or more address are marked as held via mailer which uses the hold mailer ag.

• The mail message has been marked as quarantined via a mail lter or rulesets.

2.3.1. Queue Groups and Queue Directories

There are one or more mail queues. Each mail queue belongs to a queue group. There is

always a default queue group that is called ‘‘mqueue’’ (which is where messages go by default

unless otherwise specied). The directory or directories which comprise the default queue

group are specied by the QueueDirectory option. There are zero or more additional named

queue groups declared using the Q command in the conguration le.

By default, a queued message is placed in the queue group associated with the rst recipi-

ent in the recipient list. A recipient address is mapped to a queue group as follows. First, if

there is a ruleset called ‘‘queuegroup’’, and if this ruleset maps the address to a queue group

name, then that queue group is chosen. That is, the argument for the ruleset is the recipient

address (i.e., the address part of the resolved triple) and the result should be $# followed by the

name of a queue group. Otherwise, if the mailer associated with the address species a queue

group, then that queue group is chosen. Otherwise, the default queue group is chosen.

A message with multiple recipients will be split if different queue groups are chosen by

the mapping of recipients to queue groups.

When a message is placed in a queue group, and the queue group has more than one

queue, a queue is selected randomly.

If a message with multiple recipients is placed into a queue group with the ’r’ option

(maximum number of recipients per message) set to a positive value N, and if there are more

than N recipients in the message, then the message will be split into multiple messages, each of

which have at most N recipients.

Notice: if multiple queue groups are used, do not move queue les around, e.g., into a dif-

ferent queue directory. This may have weird effects and can cause mail not to be delivered.

Queue les and directories should be treated as opaque and should not be manipulated directly.

2.3.2. Queue Runs

sendmail has two different ways to process the queue(s). The rst one is to start queue

runners after certain intervals (‘‘normal’’ queue runners), the second one is to keep queue runner

processes around (‘‘persistent’’ queue runners). How to select either of these types is discussed

in the appendix ‘‘COMMAND LINE FLAGS’’. Persistent queue runners have the advantage

that no new processes need to be spawned at certain intervals; they just sleep for a specied time

Sendmail Installation and Operation Guide

SMM:08-17

after theynished a queue run. Another advantage of persistent queue runners is that only one

process belonging to a workgroup (a workgroup is a set of queue groups) collects the data for a

queue run and then multiple queue runner may go ahead using that data. This can signicantly

reduce the disk I/O necessary to read the queue les compared to starting multiple queue run-

ners directly. Their disadvantage is that a new queue run is only started after all queue runners

belonging to a group nished their tasks. In case one of the queue runners tries delivery to a

slow recipient site at the end of a queue run, the next queue run may be substantially delayed.

In general this should be smoothed out due to the distribution of those slow jobs, however, for

sites with small number of queue entries this might introduce noticeable delays. In general, per-

sistent queue runners are only useful for sites with big queues.

2.3.3. Manual Intervention

Under normal conditions the mail queue will be processed transparently. Howev er, you

may nd that manual intervention is sometimes necessary. For example, if a major host is down

for a period of time the queue may become clogged. Although sendmail ought to recover grace-

fully when the host comes up, you may nd performance unacceptably bad in the meantime. In

that case you want to check the content of the queue and manipulate it as explained in the next

two sections.

2.3.4. Printing the queue

The contents of the queue(s) can be printed using the mailq command (or by specifying

thebpag to sendmail):

mailq

This will produce a listing of the queue id’s, the size of the message, the date the message

entered the queue, and the sender and recipients. If shared memory support is compiled in, the

agbP can be used to print the number of entries in the queue(s), provided a process updates

the data. However, as explained earlier, the output might be slightly wrong, since access to the

shared memory is not locked. For example, ‘‘unknown number of entries’’ might be shown.

The internal counters are updated after each queue run to the correct value again.

2.3.5. Forcing the queue

Sendmail should run the queue automatically at intervals. When using multiple queues, a

separate process will by default be created to run each of the queues unless the queue run is ini-

tiated by a user with the verbose ag. The algorithm is to read and sort the queue, and then to

attempt to process all jobs in order. When it attempts to run the job, sendmailrst checks to see

if the job is locked. If so, it ignores the job.

There is no attempt to insure that only one queue processor exists at any time, since there

is no guarantee that a job cannot take forever to process (however, sendmail does include heuris-

tics to try to abort jobs that are taking absurd amounts of time; technically, this violates RFC

821, but is blessed by RFC 1123). Due to the locking algorithm, it is impossible for one job to

freeze the entire queue. However, an uncooperative recipient host or a program recipient that

never returns can accumulate many processes in your system. Unfortunately, there is no com-

pletely general way to solve this.

In some cases, you may nd that a major host going down for a couple of days may create

a prohibitively large queue. This will result in sendmail spending an inordinate amount of time

sorting the queue. This situation can be xed by moving the queue to a temporary place and

creating a new queue. The old queue can be run later when the offending host returns to service.

To do this, it is acceptable to move the entire queue directory:

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Sendmail Installation and Operation Guide

cd /var/spool

mv mqueue omqueue; mkdir mqueue; chmod 0700 mqueue

You should then kill the existing daemon (since it will still be processing in the old queue direc-

tory) and create a new daemon.

To run the old mail queue, issue the following command:

/usr/sbin/sendmail C /etc/mail/queue.cf q

TheCag species an alternate conguration le queue.cf which should refer to the moved

queue directory

O QueueDirectory=/var/spool/omqueue

and theqag says to just run every job in the queue. You can also specify the moved queue

directory on the command line

/usr/sbin/sendmail oQ/var/spool/omqueue q

but this requires that you do not have queue groups in the conguration le, because those are

not subdirectories of the moved directory. See the section about ‘‘Queue Group Declaration’’

for details; you most likely need a different conguration le to correctly deal with this problem.

However, a proper conguration of queue groups should avoid lling up queue directories, so

you shouldn’t run into this problem. If you have a tendency tow ard voyeurism, you can use the

vag to watch what is going on.

When the queue is nally emptied, you can remove the directory:

rmdir /var/spool/omqueue

2.3.6. Quarantined Queue Items

It is possible to "quarantine" mail messages, otherwise known as envelopes. Envelopes

(queue les) are stored but not considered for delivery or display unless the "quarantine" state of

the envelope is undone or delivery or display of quarantined items is requested. Quarantined

messages are tagged by using a different name for the queue le, ’hf’ instead of ’qf’, and by

adding the quarantine reason to the queue le.

Delivery or display of quarantined items can be requested using theqQag to sendmail

or mailq. Additionally, messages already in the queue can be quarantined or unquarantined

using the newQag to sendmail. For example,

sendmail -Qreason -q[!][I|R|S][matchstring]

Quarantines the normal queue items matching the criteria specied by the -q[!][I|R|S][match-

string] using the reason given on theQag. Likewise,

sendmail -qQ -Q[reason] -q[!][I|R|S|Q][matchstring]

Change the quarantine reason for the quarantined items matching the criteria specied by the

-q[!][I|R|S|Q][matchstring] using the reason given on theQag. If there is no reason,

unquarantine the matching items and make them normal queue items. Note that theqQag

tells sendmail to operate on quarantined items instead of normal items.

2.4. Disk Based Connection Information

Sendmail stores a large amount of information about each remote system it has connected to

in memory. It is possible to preserve some of this information on disk as well, by using the HostSta-

tusDirectory option, so that it may be shared between several invocations of sendmail. This allows

mail to be queued immediately or skipped during a queue run if there has been a recent failure in

connecting to a remote machine. Note: information about a remote system is stored in a le whose

pathname consists of the components of the hostname in reverse order. For example, the informa-

tion for host.example.com is stored in com./example./host. For top-level domains like com this

Sendmail Installation and Operation Guide

SMM:08-19

can create a large number of subdirectories which on some lesystems can exhaust some limits.

Moreover, the performance of lookups in directory with thousands of entries can be fairly slow

depending on the lesystem implementation.

Additionally enabling SingleThreadDelivery has the added effect of single-threading mail

delivery to a destination. This can be quite helpful if the remote machine is running an SMTP

server that is easily overloaded or cannot accept more than a single connection at a time, but can

cause some messages to be punted to a future queue run. It also applies to all hosts, so setting this

because you have one machine on site that runs some software that is easily overrun can cause mail

to other hosts to be slowed down. If this option is set, you probably want to set the MinQueueAge

option as well and run the queue fairly frequently; this way jobs that are skipped because another

sendmail is talking to the same host will be tried again quickly rather than being delayed for a long

time.

The disk based host information is stored in a subdirectory of the mqueue directory called

.hoststat7. Removing this directory and its subdirectories has an effect similar to the purgestat

command and is completely safe. However, purgestat only removes expired (Timeout.hoststatus)

data. The information in these directories can be perused with the hoststat command, which will

indicate the host name, the last access, and the status of that access. An asterisk in the left most col-

umn indicates that a sendmail process currently has the host locked for mail delivery.

The disk based connection information is treated the same way as memory based connection

information for the purpose of timeouts. By default, information about host failures is valid for 30

minutes. This can be adjusted with the Timeout.hoststatus option.

The connection information stored on disk may be expired at any time with the purgestat

command or by invoking sendmail with thebH switch. The connection information may be

viewed with the hoststat command or by invoking sendmail with thebh switch.

2.5. The Service Switch

The implementation of certain system services such as host and user name lookup is con-

trolled by the service switch. If the host operating system supports such a switch, and sendmail

knows about it, sendmail will use the native version. Ultrix, Solaris, and DEC OSF/1 are examples

of such systems8.

If the underlying operating system does not support a service switch (e.g., SunOS 4.X, HP-

UX, BSD) then sendmail will provide a stub implementation. The ServiceSwitchFile option points

to the name of a le that has the service denitions. Each line has the name of a service and the

possible implementations of that service. For example, the le:

hosts

dnsles nis

aliases les nis

will ask sendmail to look for hosts in the Domain Name System rst. If the requested host name is

not found, it tries local les, and if that fails it tries NIS. Similarly, when looking for aliases it will

try the local les rst followed by NIS.

Notice: since sendmail must access MX records for correct operation, it will use DNS if it is

congured in the ServiceSwitchFilele. Hence an entry like

hosts

les dns

will not avoid DNS lookups even if a host can be found in /etc/hosts.

7This is the usual value of the HostStatusDirectory option; it can, of course, go anywhere you like in your lesystem.

8HP-UX 10 has service switch support, but since the APIs are apparently not available in the libraries sendmail does not use the

native service switch in this release.

SMM:08-20

Sendmail Installation and Operation Guide

Note: in contrast to the sendmail stub implementation some operating systems do not preserve

temporary failures. For example, if DNS returns a TRY_AGAIN status for this setup

hosts

les dns myhostname

but myhostname does not nd the requested entry, then a permanent error is returned to sendmail

which obviously can cause problems, e.g., an immediate bounce instead of a deferral.

Service switches are not completely integrated. For example, despite the fact that the host

entry listed in the above example species to look in NIS, on SunOS this won’t happen because the

system implementation of gethostbyname (3) doesn’t understand this.

2.6. The Alias Database

After recipient addresses are read from the SMTP connection or command line they are

parsed by ruleset 0, which must resolve to a {mailer, host, address} triple. If the ags selected by

the mailer include the A (aliasable) ag, the address part of the triple is looked up as the key (i.e.,

the left hand side) in the alias database. If there is a match, the address is deleted from the send

queue and all addresses on the right hand side of the alias are added in place of the alias that was

found. This is a recursive operation, so aliases found in the right hand side of the alias are similarly

expanded.

The alias database exists in two forms. One is a text form, maintained in the le

/etc/mail/aliases. The aliases are of the form

name: name1, name2, ...

Only local names may be aliased; e.g.,

eric@prep.ai.MIT.EDU: eric@CS.Berkeley.EDU

will not have the desired effect (except on prep.ai.MIT.EDU, and they probably don’t want me)9.

Aliases may be continued by starting any continuation lines with a space or a tab or by putting a

backslash directly before the newline. Blank lines and lines beginning with a sharp sign (“#”) are

comments.

The second form is processed by one of the available map types, e.g., ndbm (3)10 the Berkeley

DB library, or cdb. This is the form that sendmail actually uses to resolve aliases. This technique is

used to improve performance.

The control of search order is actually set by the service switch. Essentially, the entry

O AliasFile=switch:aliases

is always added as the rst alias entry; also, the rst alias le name without a class (e.g., without

“nis:” on the front) will be used as the name of the le for a ‘‘les’’ entry in the aliases switch. For

example, if the conguration le contains

O AliasFile=/etc/mail/aliases

and the service switch contains

aliases nisles nisplus

then aliases will rst be searched in the NIS database, then in /etc/mail/aliases, then in the NIS+

database.

You can also use NIS-based alias les. For example, the specication:

9Actually, any mailer that has the ‘A’ mailer ag set will permit aliasing; this is normally limited to the local mailer.

10The gdbm package does not work.

Sendmail Installation and Operation Guide

SMM:08-21

O AliasFile=/etc/mail/aliases

O AliasFile=nis:mail.aliases@my.nis.domain

will rst search the /etc/mail/aliases le and then the map named “mail.aliases” in “my.nis.domain”.

Warning: if you build your own NIS-based alias les, be sure to provide thelag to makedbm(8)

to map upper case letters in the keys to lower case; otherwise, aliases with upper case letters in their

names won’t match incoming addresses.

Additional ags can be added after the colon exactly like a K line — for example:

O AliasFile=nis:N mail.aliases@my.nis.domain

will search the appropriate NIS map and always include null bytes in the key. Also:

O AliasFile=nis:f mail.aliases@my.nis.domain

will prevent sendmail from downcasing the key before the alias lookup.

2.6.1. Rebuilding the alias database

The hash or dbm version of the database may be rebuilt explicitly by executing the com-

mand

newaliases

This is equivalent to giving sendmail thebiag:

/usr/sbin/sendmail bi

If you have multiple aliases databases specied, thebiag rebuilds all the database

types it understands (for example, it can rebuild NDBM databases but not NIS databases).

2.6.2. Potential problems

There are a number of problems that can occur with the alias database. They all result

from a sendmail process accessing the DBM version while it is only partially built. This can

happen under two circumstances: One process accesses the database while another process is

rebuilding it, or the process rebuilding the database dies (due to being killed or a system crash)

before completing the rebuild.

Sendmail has three techniques to try to relieve these problems. First, it ignores interrupts

while rebuilding the database; this avoids the problem of someone aborting the process leaving a

partially rebuilt database. Second, it locks the database source le during the rebuild — but that

may not work over NFS or if the le is unwritable. Third, at the end of the rebuild it adds an

alias of the form

@: @

(which is not normally legal). Before sendmail will access the database, it checks to insure that

this entry exists11.

2.6.3. List owners

If an error occurs on sending to a certain address, say “x”, sendmail will look for an alias

of the form “owner-x” to receive the errors. This is typically useful for a mailing list where the

submitter of the list has no control over the maintenance of the list itself; in this case the list

maintainer would be the owner of the list. For example:

11The AliasWait option is required in the conguration for this action to occur. This should normally be specied.

SMM:08-22

Sendmail Installation and Operation Guide

unix-wizards: eric@ucbarpa, wnj@monet, nosuchuser,

sam@matisse

owner-unix-wizards: unix-wizards-request

unix-wizards-request: eric@ucbarpa

would cause “eric@ucbarpa” to get the error that will occur when someone sends to unix-wiz-

ards due to the inclusion of “nosuchuser” on the list.

List owners also cause the envelope sender address to be modied. The contents of the

owner alias are used if they point to a single user, otherwise the name of the alias itself is used.

For this reason, and to obey Internet conventions, the “owner-” address normally points at the

“-request” address; this causes messages to go out with the typical Internet convention of using

‘‘list-request’’ as the return address.

2.7. User Information Database

This option is deprecated, use virtusertable and genericstable instead as explained in

cf/README. If you have a version of sendmail with the user information database compiled in, and

you have specied one or more databases using the U option, the databases will be searched for a

user:maildrop entry. If found, the mail will be sent to the specied address.

2.8. Per-User Forwarding (.forward Files)

As an alternative to the alias database, any user may put a le with the name “.forward” in his

or her home directory. If this le exists, sendmail redirects mail for that user to the list of addresses

listed in the .forward le. Note that aliases are fully expanded before forward les are referenced.

For example, if the home directory for user “mckusick” has a .forward le with contents:

mckusick@ernie

kirk@calder

then any mail arriving for “mckusick” will be redirected to the specied accounts.

Actually, the conguration le denes a sequence of lenames to check. By default, this is

the user’s .forward le, but can be dened to be more generally using the ForwardPath option. If

you change this, you will have to inform your user base of the change; .forward is pretty well incor-

porated into the collective subconscious.

2.9. Special Header Lines

Several header lines have special interpretations dened by the conguration le. Others

have interpretations built into sendmail that cannot be changed without changing the code. These

built-ins are described here.

2.9.1. Errors-To:

If errors occur anywhere during processing, this header will cause error messages to go to

the listed addresses. This is intended for mailing lists.

The Errors-To: header was created in the bad old days when UUCP didn’t understand the

distinction between an envelope and a header; this was a hack to provide what should now be

passed as the envelope sender address. It should go away. It is only used if the UseErrorsTo

option is set.

The Errors-To: header is ofcially deprecated and will go away in a future release.

2.9.2. Apparently-To:

RFC 822 requires at least one recipient eld (To:, Cc:, or Bcc: line) in every message. If a

message comes in with no recipients listed in the message then sendmail will adjust the header

based on the “NoRecipientAction” option. One of the possible actions is to add an “Apparently-

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SMM:08-23

To:” header line for any recipients it is aware of.

The Apparently-To: header is non-standard and is both deprecated and strongly discour-

aged.

2.9.3. Precedence

The Precedence: header can be used as a crude control of message priority. It tweaks the

sort order in the queue and can be congured to change the message timeout values. The prece-

dence of a message also controls how delivery status notications (DSNs) are processed for that

message.

2.10. IDENT Protocol Support

Sendmail supports the IDENT protocol as dened in RFC 1413. Note that the RFC states a

client should wait at least 30 seconds for a response. The default Timeout.ident is 5 seconds as

many sites have adopted the practice of dropping IDENT queries. This has lead to delays process-

ing mail. Although this enhances identication of the author of an email message by doing a ‘‘call

back’’ to the originating system to include the owner of a particular TCP connection in the audit

trail it is in no sense perfect; a determined forger can easily spoof the IDENT protocol. The follow-

ing description is excerpted from RFC 1413:

6. Security Considerations

The information returned by this protocol is at most as trustworthy as the host providing it OR

the organization operating the host. For example, a PC in an open lab has few if any controls

on it to prevent a user from having this protocol return any identier the user wants. Like-

wise, if the host has been compromised the information returned may be completely erro-

neous and misleading.

The Identication Protocol is not intended as an authorization or access control protocol. At

best, it provides some additional auditing information with respect to TCP connections. At

worst, it can provide misleading, incorrect, or maliciously incorrect information.

The use of the information returned by this protocol for other than auditing is strongly dis-

couraged. Specically, using Identication Protocol information to make access control deci-

sions - either as the primary method (i.e., no other checks) or as an adjunct to other methods

may result in a weakening of normal host security.

An Identication server may reveal information about users, entities, objects or processes

which might normally be considered private. An Identication server provides service which

is a rough analog of the CallerID services provided by some phone companies and many of

the same privacy considerations and arguments that apply to the CallerID service apply to

Identication. If you wouldn’t run a "nger" server due to privacy considerations you may

not want to run this protocol.

In some cases your system may not work properly with IDENT support due to a bug in the TCP/IP

implementation. The symptoms will be that for some hosts the SMTP connection will be closed

almost immediately. If this is true or if you do not want to use IDENT, you should set the IDENT

timeout to zero; this will disable the IDENT protocol.

3. ARGUMENTS

The complete list of arguments to sendmail is described in detail in Appendix A. Some important

arguments are described here.

3.1. Queue Interval

The amount of time between forking a process to run through the queue is dened by theq

ag. If you run with delivery mode set to i or b this can be relatively large, since it will only be

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Sendmail Installation and Operation Guide

relevant when a host that was down comes back up. If you run in q mode it should be relatively

short, since it denes the maximum amount of time that a message may sit in the queue. (See also

the MinQueueAge option.)

RFC 1123 section 5.3.1.1 says that this value should be at least 30 minutes (although that

probably doesn’t make sense if you use ‘‘queue-only’’ mode).

Notice: the meaning of the interval time depends on whether normal queue runners or persis-

tent queue runners are used. For the former, it is the time between subsequent starts of a queue run.

For the latter, it is the time sendmail waits after a persistent queue runner has nished its work to

start the next one. Hence for persistent queue runners this interval should be very low, typically no

more than two minutes.

3.2. Daemon Mode

If you allow incoming mail over an IPC connection, you should have a daemon running. This

should be set by your /etc/rcle using thebdag. Thebdag and theqag may be combined

in one call:

/usr/sbin/sendmail bd q30m

An alternative approach is to invoke sendmail from inetd(8) (use thebsAm ags to ask

sendmail to speak SMTP on its standard input and output and to run as MTA). This works and

allows you to wrap sendmail in a TCP wrapper program, but may be a bit slower since the congu-

ration le has to be re-read on every message that comes in. If you do this, you still need to have a

sendmail running to ush the queue:

/usr/sbin/sendmail q30m

3.3. Forcing the Queue

In some cases you may nd that the queue has gotten clogged for some reason. You can force

a queue run using theqag (with no value). It is entertaining to use thevag (verbose) when

this is done to watch what happens:

/usr/sbin/sendmail q v

You can also limit the jobs to those with a particular queue identier, recipient, sender, quar-

antine reason, or queue group using one of the queue modiers. For example, “qRberkeley”

restricts the queue run to jobs that have the string “berkeley” somewhere in one of the recipient

addresses. Similarly, “qSstring” limits the run to particular senders, “qIstring” limits it to partic-

ular queue identiers, and “qQstring” limits it to particular quarantined reasons and only operated

on quarantined queue items, and “qGstring” limits it to a particular queue group. The named

queue group will be run even if it is set to have 0 runners. You may also place an ! before the I or

R or S or Q to indicate that jobs are limited to not including a particular queue identier, recipient

or sender. For example, “q!Rseattle” limits the queue run to jobs that do not have the string “seat-

tle” somewhere in one of the recipient addresses. Should you need to terminate the queue jobs cur-

rently active then a SIGTERM to the parent of the process (or processes) will cleanly stop the jobs.

3.4. Debugging

There are a fairly large number of debug ags built into sendmail. Each debug ag has a cat-

egory and a level. Higher levels increase the level of debugging activity; in most cases, this means

to print out more information. The convention is that levels greater than nine are “absurd,” i.e., they

print out so much information that you wouldn’t normally want to see them except for debugging

that particular piece of code.

You should never run a production sendmail server in debug mode. Many of the debug ags

will result in debug output being sent over the SMTP channel unless the optionD is used. This

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SMM:08-25

will confuse many mail programs. However, for testing purposes, it can be useful when sending

mail manually via telnet to the port you are using while debugging.

A debug category is either an integer, like 42, or a name, like ANSI. You can specify a range

of numeric debug categories using the syntax 17-42. You can specify a set of named debug cate-

gories using a glob pattern like “sm_trace_*”. At present, only “*” and “?” are supported in these

glob patterns.

Debug ags are set using thed option; the syntax is:

debug-ag:

d debug-list

debug-list:

debug-option [ , debug-option ]*

debug-option:

debug-categories [ . debug-level ]

debug-categories:

integer | integer integer | category-pattern

category-pattern:

[a-zA-Z_*?][a-zA-Z0-9_*?]*

debug-level:

integer

where spaces are for reading ease only. For example,

d12

Set category 12 to level 1

d12.3

Set category 12 to level 3

d317

Set categories 3 through 17 to level 1

d317.4

Set categories 3 through 17 to level 4

dANSI

Set category ANSI to level 1

dsm_trace_*.3

Set all named categories matching sm_trace_* to level 3

For a complete list of the available debug ags you will have to look at the code and the TRACE-

FLAGSle in the sendmail distribution (they are too dynamic to keep this document up to date).

For a list of named debug categories in the sendmail binary, use

ident /usr/sbin/sendmail | grep Debug

3.5. Changing the Values of Options

Options can be overridden using theo orO command line ags. For example,

/usr/sbin/sendmail oT2m

sets the T (timeout) option to two minutes for this run only; the equivalent line using the long option

name is

/usr/sbin/sendmail -OTimeout.queuereturn=2m

Some options have security implications. Sendmail allows you to set these, but relinquishes

its set-user-ID or set-group-ID permissions thereafter12.

3.6. Trying a Different Conguration File

An alternative conguration le can be specied using theCag; for example,

/usr/sbin/sendmail Ctest.cf oQ/tmp/mqueue

uses the conguration le test.cf instead of the default /etc/mail/sendmail.cf. If theCag has no

value it defaults to sendmail.cf in the current directory.

Sendmail gives up set-user-ID root permissions (if it has been installed set-user-ID root) when

you use this ag, so it is common to use a publicly writable directory (such as /tmp) as the queue

directory (QueueDirectory or Q option) while testing.

12That is, it sets its effective uid to the real uid; thus, if you are executing as root, as from root’s crontab le or during system

startup the root permissions will still be honored.

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Sendmail Installation and Operation Guide

3.7. Logging Trafc

Many SMTP implementations do not fully implement the protocol. For example, some per-

sonal computer based SMTPs do not understand continuation lines in reply codes. These can be

very hard to trace. If you suspect such a problem, you can set trafc logging using theXag. For

example,

/usr/sbin/sendmail X /tmp/trafc bd

will log all trafc in the le /tmp/trafc.

This logs a lot of data very quickly and should NEVER be used during normal operations.

After starting up such a daemon, force the errant implementation to send a message to your host.

All message trafc in and out of sendmail, including the incoming SMTP trafc, will be logged in

this le.

3.8. Testing Conguration Files

When you build a conguration table, you can do a certain amount of testing using the “test

mode” of sendmail. For example, you could invoke sendmail as:

sendmail bt Ctest.cf

which would read the conguration le “test.cf” and enter test mode. In this mode, you enter lines

of the form:

rwset address

where rwset is the rewriting set you want to use and address is an address to apply the set to. Test

mode shows you the steps it takes as it proceeds, nally showing you the address it ends up with.

You may use a comma separated list of rwsets for sequential application of rules to an input. For

example:

3,1,21,4 monet:bollard

rst applies ruleset three to the input “monet:bollard.” Ruleset one is then applied to the output of

ruleset three, followed similarly by rulesets twenty-one and four.

If you need more detail, you can also use the “d21” ag to turn on more debugging. For

example,

sendmail bt d21.99

turns on an incredible amount of information; a single word address is probably going to print out

several pages worth of information.

You should be warned that internally, sendmail applies ruleset 3 to all addresses. In test mode

you will have to do that manually. For example, older versions allowed you to use

0 bruce@broadcast.sony.com

This version requires that you use:

3,0 bruce@broadcast.sony.com

As of version 8.7, some other syntaxes are available in test mode:

.D x value

denes macro x to have the indicated value. This is useful when debugging rules

that use the $&x syntax.

.C c value

adds the indicated value to class c.

=S ruleset

dumps the contents of the indicated ruleset.

d debug-spec

is equivalent to the command-line ag.

Version 8.9 introduced more features:

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SMM:08-27

?

shows a help message.

=M

display the known mailers.

$m

print the value of macro m.

$=c

print the contents of class c.

/mx host

returns the MX records for ‘host’.

/parse address

parse address, returning the value of crackaddr, and the parsed address.

/try mailer addr

rewrite address into the form it will have when presented to the indicated mailer.

/tryags ags

set ags used by parsing. The ags can be ‘H’ for Header or ‘E’ for Envelope,

and ‘S’ for Sender or ‘R’ for Recipient. These can be combined, ‘HR’ sets ags

for header recipients.

/canon hostname try to canonify hostname.

/map mapname key

look up ‘key’ in the indicated ‘mapname’.

/quit

quit address test mode.

3.9. Persistent Host Status Information

When HostStatusDirectory is enabled, information about the status of hosts is maintained on

disk and can thus be shared between different instantiations of sendmail. The status of the last con-

nection with each remote host may be viewed with the command:

sendmail bh

This information may be ushed with the command:

sendmail bH

Flushing the information prevents new sendmail processes from loading it, but does not prevent

existing processes from using the status information that they already have.

4. TUNING

There are a number of conguration parameters you may want to change, depending on the

requirements of your site. Most of these are set using an option in the conguration le. For example,

the line “O Timeout.queuereturn=5d” sets option “Timeout.queuereturn” to the value “5d” (ve days).

Most of these options have appropriate defaults for most sites. However, sites having very high

mail loads may nd they need to tune them as appropriate for their mail load. In particular, sites experi-

encing a large number of small messages, many of which are delivered to many recipients, may nd

that they need to adjust the parameters dealing with queue priorities.

All versions of sendmail prior to 8.7 had single character option names. As of 8.7, options have

long (multi-character names). Although old short names are still accepted, most new options do not

have short equivalents.

This section only describes the options you are most likely to want to tweak; read section 5 for

more details.

4.1. Timeouts

All time intervals are set using a scaled syntax. For example, “10m” represents ten minutes,

whereas “2h30m” represents two and a half hours. The full set of scales is:

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Sendmail Installation and Operation Guide

s

seconds

m

minutes

h

hours

d

days

w

weeks

4.1.1. Queue interval

The argument to theqag species how often a sub-daemon will run the queue. This is

typically set to between fteen minutes and one hour. If not set, or set to zero, the queue will

not be run automatically. RFC 1123 section 5.3.1.1 recommends that this be at least 30 minutes.

Should you need to terminate the queue jobs currently active then a SIGTERM to the parent of

the process (or processes) will cleanly stop the jobs.

4.1.2. Read timeouts

Timeouts all have option names “Timeout.suboption”. Most of these control SMTP oper-

ations. The recognized suboptions, their default values, and the minimum values allowed by

RFC 2821 section 4.5.3.2 (or RFC 1123 section 5.3.2) are:

connect

The time to wait for an SMTP connection to open (the connect(2) system call)

[0, unspecied]. If zero, uses the kernel default. In no case can this option

extend the timeout longer than the kernel provides, but it can shorten it. This

is to get around kernels that provide an absurdly long connection timeout (90

minutes in one case).

iconnect

The same as connect, except it applies only to the initial attempt to connect to

a host for a given message [0, unspecied]. The concept is that this should be

very short (a few seconds); hosts that are well connected and responsive will

thus be serviced immediately. Hosts that are slow will not hold up other deliv-

eries in the initial delivery attempt.

aconnect

[0, unspecied] The overall timeout waiting for all connection for a single

delivery attempt to succeed. If 0, no overall limit is applied. This can be used

to restrict the total amount of time trying to connect to a long list of host that

could accept an e-mail for the recipient. This timeout does not apply to Fall-

backMXhost, i.e., if the time is exhausted, the FallbackMXhost is tried next.

initial

The wait for the initial 220 greeting message [5m, 5m].

helo

The wait for a reply from a HELO or EHLO command [5m, unspecied].

This may require a host name lookup, so ve minutes is probably a reasonable

minimum.

mail†

The wait for a reply from a MAIL command [10m, 5m].

rcpt†

The wait for a reply from a RCPT command [1h, 5m]. This should be long

because it could be pointing at a list that takes a long time to expand (see

below).

datainit†

The wait for a reply from a DAT A command [5m, 2m].

datablock†‡

The wait for reading a data block (that is, the body of the message). [1h, 3m].

This should be long because it also applies to programs piping input to send-

mail which have no guarantee of promptness.

datanal†

The wait for a reply from the dot terminating a message. [1h, 10m]. If this is

shorter than the time actually needed for the receiver to deliver the message,

duplicates will be generated. This is discussed in RFC 1047.

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rset

The wait for a reply from a RSET command [5m, unspecied].

quit

The wait for a reply from a QUIT command [2m, unspecied].

misc

The wait for a reply from miscellaneous (but short) commands such as NOOP

(no-operation) and VERB (go into verbose mode). [2m, unspecied].

command†‡

In server SMTP, the time to wait for another command. [1h, 5m].

ident‡

The timeout waiting for a reply to an IDENT query [5s13, unspecied].

lhlo

The wait for a reply to an LMTP LHLO command [2m, unspecied].

auth

The timeout for a reply in an SMTP AUTH dialogue [10m, unspecied].

starttls

The timeout for a reply to an SMTP STARTTLS command and the TLS hand-

shake [1h, unspecied].

leopen‡

The timeout for opening .forward and :include: les [60s, none].

control‡

The timeout for a complete control socket transaction to complete [2m, none].

hoststatus‡

How long status information about a host (e.g., host down) will be cached

before it is considered stale [30m, unspecied].

resolver.retrans‡ The resolver’s retransmission time interval (in seconds) [varies]. Sets both

Timeout.resolver.retrans.rst and Timeout.resolver.retrans.normal.

resolver.retrans.rst‡

The resolver’s retransmission time interval (in seconds) for the rst attempt to

deliver a message [varies].

resolver.retrans.normal‡

The resolver’s retransmission time interval (in seconds) for all resolver

lookups except the rst delivery attempt [varies].

resolver.retry‡

The number of times to retransmit a resolver query.

Sets both Time-

out.resolver.retry.rst and Timeout.resolver.retry.normal [varies].

resolver.retry.rst‡

The number of times to retransmit a resolver query for the rst attempt to

deliver a message [varies].

resolver.retry.normal‡

The number of times to retransmit a resolver query for all resolver lookups

except the rst delivery attempt [varies].

For compatibility with old conguration les, if no suboption is specied, all the timeouts

marked with a dagger (†) are set to the indicated value. All but those marked with a double dag-

ger (‡) apply to client SMTP.

For example, the lines:

O Timeout.command=25m

O Timeout.datablock=3h

sets the server SMTP command timeout to 25 minutes and the input data block timeout to three

hours.

4.1.3. Message timeouts

After sitting in the queue for a few days, an undeliverable message will time out. This is

to insure that at least the sender is aware of the inability to send a message. The timeout is

13On some systems the default is zero to turn the protocol off entirely.

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Sendmail Installation and Operation Guide

typically set to ve days. It is sometimes considered convenient to also send a warning message

if the message is in the queue longer than a few hours (assuming you normally have good con-

nectivity; if your messages normally took several hours to send you wouldn’t want to do this

because it wouldn’t be an unusual event). These timeouts are set using the Timeout.queuere-

turn and Timeout.queuewarn options in the conguration le (previously both were set using

the T option).

If the message is submitted using the NOTIFY SMTP extension, warning messages will

only be sent if NOTIFY=DELAY is specied. The queuereturn and queuewarn timeouts can be

further qualied with a tag based on the Precedence: eld in the message; they must be one of

“urgent” (indicating a positive non-zero precedence), “normal” (indicating a zero precedence),

or “non-urgent” (indicating negative precedences). For example, setting “Timeout.queue-

warn.urgent=1h” sets the warning timeout for urgent messages only to one hour. The default if

no precedence is indicated is to set the timeout for all precedences. If the message has a normal

(default) precedence and it is a delivery status notication (DSN), Timeout.queuereturn.dsn

and Timeout.queuewarn.dsn can be used to give an alternative warn and return time for DSNs.

The value "now" can be used for -O Timeout.queuereturn to return entries immediately during a

queue run, e.g., to bounce messages independent of their time in the queue.

Since these options are global, and since you cannot know a priori how long another host

outside your domain will be down, a ve day timeout is recommended. This allows a recipient

to x the problem even if it occurs at the beginning of a long weekend. RFC 1123 section

5.3.1.1 says that this parameter should be ‘‘at least 45 days’’.

The Timeout.queuewarn value can be piggybacked on the T option by indicating a time

after which a warning message should be sent; the two timeouts are separated by a slash. For

example, the line

OT5d/4h

causes email to fail after ve days, but a warning message will be sent after four hours. This

should be large enough that the message will have been tried several times.

4.2. Forking During Queue Runs

By setting the ForkEachJob (Y) option, sendmail will fork before each individual message

while running the queue. This option was used with earlier releases to prevent sendmail from con-

suming large amounts of memory. It should no longer be necessary with sendmail 8.12. If the

ForkEachJob option is not set, sendmail will keep track of hosts that are down during a queue run,

which can improve performance dramatically.

If the ForkEachJob option is set, sendmail cannot use connection caching.

4.3. Queue Priorities

Every message is assigned a priority when it is rst instantiated, consisting of the message

size (in bytes) offset by the message class (which is determined from the Precedence: header) times

the “work class factor” and the number of recipients times the “work recipient factor.” The priority

is used to order the queue. Higher numbers for the priority mean that the message will be processed

later when running the queue.

The message size is included so that large messages are penalized relative to small messages.

The message class allows users to send “high priority” messages by including a “Precedence:” eld

in their message; the value of this eld is looked up in the P lines of the conguration le. Since the

number of recipients affects the amount of load a message presents to the system, this is also

included into the priority.

The recipient and class factors can be set in the conguration le using the RecipientFactor

(y) and ClassFactor (z) options respectively. They default to 30000 (for the recipient factor) and

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1800 (for the class factor). The initial priority is:

pri = msgsize (class × ClassFactor) + (nrcpt × RecipientFactor)

(Remember, higher values for this parameter actually mean that the job will be treated with lower

priority.)

The priority of a job can also be adjusted each time it is processed (that is, each time an

attempt is made to deliver it) using the “work time factor,” set by the RetryFactor (Z) option. This

is added to the priority, so it normally decreases the precedence of the job, on the grounds that jobs

that have failed many times will tend to fail again in the future. The RetryFactor option defaults to

90000.

4.4. Load Limiting

Sendmail can be asked to queue (but not deliver) mail if the system load average gets too high

using the QueueLA (x) option. When the load average exceeds the value of the QueueLA option,

the delivery mode is set to q (queue only) if the QueueFactor (q) option divided by the difference

in the current load average and the QueueLA option plus one is less than the priority of the message

— that is, the message is queued iff:

pri >

QueueFactor

LA QueueLA +1

The QueueFactor option defaults to 600000, so each point of load average is worth 600000 priority

points (as described above).

For drastic cases, the RefuseLA (X) option denes a load average at which sendmail will

refuse to accept network connections. Locally generated mail, i.e., mail which is not submitted via

SMTP (including incoming UUCP mail), is still accepted. Notice that the MSP submits mail to the

MTA via SMTP, and hence mail will be queued in the client queue in such a case. Therefore it is

necessary to run the client mail queue periodically.

4.5. Resource Limits

Sendmail has several parameters to control resource usage. Besides those mentioned in the

previous

section,

there

are

at

least

MaxDaemonChildren,

ConnectionRateThrottle,

MaxQueueChildren, and MaxRunnersPerQueue. The latter two limit the number of sendmail

processes that operate on the queue. These are discussed in the section ‘‘Queue Group Declara-

tion’’. The former two can be used to limit the number of incoming connections. Their appropriate

values depend on the host operating system and the hardware, e.g., amount of memory. In many sit-

uations it might be useful to set limits to prevent to have too many sendmail processes, however,

these limits can be abused to mount a denial of service attack. For example, if MaxDaemonChil-

dren=10 then an attacker needs to open only 10 SMTP sessions to the server, leave them idle for

most of the time, and no more connections will be accepted. If this option is set then the timeouts

used in a SMTP session should be lowered from their default values to their minimum values as

specied in RFC 2821 and listed in section 4.1.2.

4.6. Measures against Denial of Service Attacks

Sendmail has some built-in measures against simple denial of service (DoS) attacks. The

SMTP server by default slows down if too many bad commands are issued or if some commands

are repeated too often within a session. Details can be found in the source le sendmail/srvrsmtp.c

by looking for the macro denitions of MAXBADCOMMANDS, MAXNOOPCOMMANDS,

MAXHELOCOMMANDS, MAXVRFYCOMMANDS, and MAXETRNCOMMANDS. If an

SMTP command is issued more often than the corresponding MAXcmdCOMMANDS value, then

the response is delayed exponentially, starting with a sleep time of one second, up to a maximum of

four minutes (as dened by MAXTIMEOUT). If the option MaxDaemonChildren is set to a

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Sendmail Installation and Operation Guide

value greater than zero, then this could make a DoS attack even worse since it keeps a connection

open longer than necessary. Therefore a connection is terminated with a 421 SMTP reply code if

the number of commands exceeds the limit by a factor of two and MAXBADCOMMANDS is set

to a value greater than zero (the default is 25).

4.7. Delivery Mode

There are a number of delivery modes that sendmail can operate in, set by the DeliveryMode

(d) conguration option. These modes specify how quickly mail will be delivered. Legal modes

are:

i

deliver interactively (synchronously)

b

deliver in background (asynchronously)

q

queue only (don’t deliver)

d

defer delivery attempts (don’t deliver)

There are tradeoffs. Mode “i” gives the sender the quickest feedback, but may slow down some

mailers and is hardly ever necessary. Mode “b” delivers promptly but can cause large numbers of

processes if you have a mailer that takes a long time to deliver a message. Mode “q” minimizes the

load on your machine, but means that delivery may be delayed for up to the queue interval. Mode

“d” is identical to mode “q” except that it also prevents lookups in maps including the -Dag from

working during the initial queue phase; it is intended for ‘‘dial on demand’’ sites where DNS

lookups might cost real money. Some simple error messages (e.g., host unknown during the SMTP

protocol) will be delayed using this mode. Mode “b” is the usual default.

If you run in mode “q” (queue only), “d” (defer), or “b” (deliver in background) sendmail will

not expand aliases and follow .forward les upon initial receipt of the mail. This speeds up the

response to RCPT commands. Mode “i” should not be used by the SMTP server.

4.8. Log Level

The level of logging can be set for sendmail. The default using a standard conguration is

level 9. The levels are approximately as follows (some log types are using different level depending

on various factors):

0

Minimal logging.

1

Serious system failures and potential security problems.

2

Lost communications (network problems) and protocol failures.

3

Other serious failures, malformed addresses, transient forward/include errors, connection

timeouts.

4

Minor failures, out of date alias databases, connection rejections via check_ rulesets.

5

Message collection statistics.

6

Creation of error messages, VRFY and EXPN commands.

7

Delivery failures (host or user unknown, etc.).

8

Successful deliveries and alias database rebuilds.

9

Messages being deferred (due to a host being down, etc.).

10

Database expansion (alias, forward, and userdb lookups) and authentication information.

11

NIS errors and end of job processing.

12

Logs all SMTP connections.

13

Log bad user shells, les with improper permissions, and other questionable situations.

14

Logs refused connections.

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15

Log all incoming SMTP commands.

20

Logs attempts to run locked queue les. These are not errors, but can be useful to note if

your queue appears to be clogged.

30

Lost locks (only if using lockf instead of ock).

Additionally, values above 64 are reserved for extremely verbose debugging output. No normal site

would ever set these.

4.9. File Modes

The modes used for les depend on what functionality you want and the level of security you

require. In many cases sendmail does careful checking of the modes of les and directories to avoid

accidental compromise; if you want to make it possible to have group-writable support les you

may need to use the DontBlameSendmail option to turn off some of these checks.

4.9.1. To suid or not to suid?

Sendmail is no longer installed set-user-ID to root. sendmail/SECURITY explains how to

congure and install sendmail without set-user-ID to root but set-group-ID which is the default

conguration starting with 8.12.

The daemon usually runs as root, unless other measures are taken. At the point where

sendmail is about to exec (2) a mailer, it checks to see if the userid is zero (root); if so, it resets

the userid and groupid to a default (set by the U= equate in the mailer line; if that is not set, the

DefaultUser option is used). This can be overridden by setting the Sag to the mailer for mail-

ers that are trusted and must be called as root. However, this will cause mail processing to be

accounted (using sa (8)) to root rather than to the user sending the mail.

A middle ground is to set the RunAsUser option. This causes sendmail to become the

indicated user as soon as it has done the startup that requires root privileges (primarily, opening

the SMTP socket). If you use RunAsUser, the queue directory (normally /var/spool/mqueue)

should be owned by that user, and all les and databases (including user .forwardles, alias

les, :include: les, and external databases) must be readable by that user. Also, since sendmail

will not be able to change its uid, delivery to programs or les will be marked as unsafe, e.g.,

undeliverable, in .forward, aliases, and :include: les. Administrators can override this by set-

ting the DontBlameSendmail option to the setting NonRootSafeAddr. RunAsUser is proba-

bly best suited for rewall congurations that don’t hav e regular user logins. If the option is

used on a system which performs local delivery, then the local delivery agent must have the

proper permissions (i.e., usually set-user-ID root) since it will be invoked by the RunAsUser,

not by root.

4.9.2. Turning off security checks

Sendmail is very particular about the modes of les that it reads or writes. For example,

by default it will refuse to read most les that are group writable on the grounds that they might

have been tampered with by someone other than the owner; it will even refuse to read les in

group writable directories. Also, sendmail will refuse to create a new aliases database in an

unsafe directory. You can get around this by manually creating the database le as a trusted user

ahead of time and then rebuilding the aliases database with newaliases.

If you are quite sure that your conguration is safe and you want sendmail to avoid these

security checks, you can turn off certain checks using the DontBlameSendmail option. This

option takes one or more names that disable checks. In the descriptions that follow, “unsafe

directory” means a directory that is writable by anyone other than the owner. The values are:

Safe

No special handling.

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Sendmail Installation and Operation Guide

AssumeSafeChown

Assume that the chown system call is restricted to root. Since some versions of UNIX

permit regular users to give away their les to other users on some lesystems, send-

mail often cannot assume that a givenle was created by the owner, particularly when

it is in a writable directory. You can set this ag if you know that le giveaw ay is

restricted on your system.

CertOwner

Accept certicate public and private key les which are not owned by RunAsUser for

STARTTLS.

ClassFileInUnsafeDirPath

When reading class les (using the F line in the conguration le), allowles that are

in unsafe directories.

DontWarnForwardFileInUnsafeDirPath

Prevent logging of unsafe directory path warnings for non-existent forward les.

ErrorHeaderInUnsafeDirPath

Allow the le named in the ErrorHeader option to be in an unsafe directory.

FileDeliveryToHardLink

Allow delivery to les that are hard links.

FileDeliveryToSymLink

Allow delivery to les that are symbolic links.

ForwardFileInGroupWritableDirPath

Allow .forwardles in group writable directories.

ForwardFileInUnsafeDirPath

Allow .forwardles in unsafe directories.

ForwardFileInUnsafeDirPathSafe

Allow a .forwardle that is in an unsafe directory to include references to program and

les.

GroupReadableKeyFile

Accept a group-readable key le for STARTTLS.

GroupReadableSASLDBFile

Accept a group-readable Cyrus SASL password le.

GroupReadableDefaultAuthInfoFile

Accept a group-readable DefaultAuthInfo le for SASL.

GroupWritableAliasFile

Allow group-writable alias les.

GroupWritableDirPathSafe

Change the denition of “unsafe directory” to consider group-writable directories to be

safe. World-writable directories are always unsafe.

GroupWritableForwardFile

Allow group writable .forwardles.

GroupWritableForwardFileSafe

Accept group-writable .forwardles as safe for program and le delivery.

GroupWritableIncludeFile

Allow group writable :include:les.

GroupWritableIncludeFileSafe

Accept group-writable :include:les as safe for program and le delivery.

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GroupWritableSASLDBFile

Accept a group-writable Cyrus SASL password le.

HelpFileInUnsafeDirPath

Allow the le named in the HelpFile option to be in an unsafe directory.

IncludeFileInGroupWritableDirPath

Allow :include:les in group writable directories.

IncludeFileInUnsafeDirPath

Allow :include:les in unsafe directories.

IncludeFileInUnsafeDirPathSafe

Allow a :include:le that is in an unsafe directory to include references to program

and les.

InsufcientEntropy

Try to use STARTTLS even if the PRNG for OpenSSL is not properly seeded despite

the security problems.

LinkedAliasFileInWritableDir

Allow an alias le that is a link in a writable directory.

LinkedClassFileInWritableDir

Allow class les that are links in writable directories.

LinkedForwardFileInWritableDir

Allow .forwardles that are links in writable directories.

LinkedIncludeFileInWritableDir

Allow :include:les that are links in writable directories.

LinkedMapInWritableDir

Allow map les that are links in writable directories. This includes alias database les.

LinkedServiceSwitchFileInWritableDir

Allow the service switch le to be a link even if the directory is writable.

MapInUnsafeDirPath

Allow maps (e.g., hash, btree, and dbmles) in unsafe directories. This includes alias

database les.

NonRootSafeAddr

Do not mark le and program deliveries as unsafe if sendmail is not running with root

privileges.

RunProgramInUnsafeDirPath

Run programs that are in writable directories without logging a warning.

RunWritableProgram

Run programs that are group- or world-writable without logging a warning.

TrustStickyBit

Allow group or world writable directories if the sticky bit is set on the directory. Do

not set this on systems which do not honor the sticky bit on directories.

WorldWritableAliasFile

Accept world-writable alias les.

WorldWritableForwardle

Allow world writable .forwardles.

WorldWritableIncludele

Allow world writable :include:les.

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Sendmail Installation and Operation Guide

WriteMapToHardLink

Allow writes to maps that are hard links.

WriteMapToSymLink

Allow writes to maps that are symbolic links.

WriteStatsToHardLink

Allow the status le to be a hard link.

WriteStatsToSymLink

Allow the status le to be a symbolic link.

4.10. Connection Caching

When processing the queue, sendmail will try to keep the last few open connections open to

avoid startup and shutdown costs. This only applies to IPC and LPC connections.

When trying to open a connection the cache is rst searched. If an open connection is found,

it is probed to see if it is still active by sending a RSET command. It is not an error if this fails;

instead, the connection is closed and reopened.

Tw o parameters control the connection cache. The ConnectionCacheSize (k) option denes

the number of simultaneous open connections that will be permitted. If it is set to zero, connections

will be closed as quickly as possible. The default is one. This should be set as appropriate for your

system size; it will limit the amount of system resources that sendmail will use during queue runs.

Never set this higher than 4.

The ConnectionCacheTimeout (K) option species the maximum time that any cached con-

nection will be permitted to idle. When the idle time exceeds this value the connection is closed.

This number should be small (under ten minutes) to prevent you from grabbing too many resources

from other hosts. The default is ve minutes.

4.11. Name Server Access

Control of host address lookups is set by the hosts service entry in your service switch le. If

you are on a system that has built-in service switch support (e.g., Ultrix, Solaris, or DEC OSF/1)

then your system is probably congured properly already. Otherwise, sendmail will consult the le

/etc/mail/service.switch, which should be created. Sendmail only uses two entries: hosts and

aliases, although system routines may use other services (notably the passwd service for user name

lookups by getpwname).

However, some systems (such as SunOS 4.X) will do DNS lookups regardless of the setting

of the service switch entry. In particular, the system routine gethostbyname(3) is used to look up

host names, and many vendor versions try some combination of DNS, NIS, and le lookup in

/etc/hosts without consulting a service switch. Sendmail makes no attempt to work around this

problem, and the DNS lookup will be done anyway. If you do not have a nameserver congured at

all, such as at a UUCP-only site, sendmail will get a “connection refused” message when it tries to

connect to the name server. If the hosts switch entry has the service “dns” listed somewhere in the

list, sendmail will interpret this to mean a temporary failure and will queue the mail for later pro-

cessing; otherwise, it ignores the name server data.

The same technique is used to decide whether to do MX lookups. If you want MX support,

you must have “dns” listed as a service in the hosts switch entry.

The ResolverOptions (I) option allows you to tweak name server options. The command

line takes a series of ags as documented in resolver(3) (with the leading “RES_” deleted). Each

can be preceded by an optional ‘+’ or ‘’. For example, the line

O ResolverOptions=+AAONLYDNSRCH

turns on the AAONLY (accept authoritative answers only) and turns off the DNSRCH (search the

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domain path) options. Most resolver libraries default DNSRCH, DEFNAMES, and RECURSE

ags on and all others off. If NETINET6 is enabled, most libraries default to USE_INET6 as well.

You can also include “HasWildcardMX” to specify that there is a wildcard MX record matching

your domain; this turns off MX matching when canonifying names, which can lead to inappropriate

canonications. Use “WorkAroundBrokenAAAA” when faced with a broken nameserver that

returns SERVFAIL (a temporary failure) on T_AAAA (IPv6) lookups during hostname canonica-

tion. Notice: it might be necessary to apply the same (or similar) options to submit.cf too.

Version level 1 congurations (see the section about ‘‘Conguration Version Level’’) turn

DNSRCH and DEFNAMES off when doing delivery lookups, but leave them on everywhere else.

Version 8 of sendmail ignores them when doing canonication lookups (that is, when using $[ ...

$]), and always does the search. If you don’t want to do automatic name extension, don’t call $[ ...

$].

The search rules for $[ ... $] are somewhat different than usual. If the name being looked up

has at least one dot, it always tries the unmodied name rst. If that fails, it tries the reduced search

path, and lastly tries the unmodied name (but only for names without a dot, since names with a dot

have already been tried). This allows names such as ‘‘utc.CS’’ to match the site in Czechoslovakia

rather than the site in your local Computer Science department. It also prefers A and CNAME

records over MX records — that is, if it nds an MX record it makes note of it, but keeps looking.

This way, if you have a wildcard MX record matching your domain, it will not assume that all

names match.

To completely turn off all name server access on systems without service switch support

(such as SunOS 4.X) you will have to recompile with DNAMED_BIND=0 and remove lresolv

from the list of libraries to be searched when linking.

4.12. Moving the Per-User Forward Files

Some sites mount each user’s home directory from a local disk on their workstation, so that

local access is fast. However, the result is that .forward le lookups from a central mail server are

slow. In some cases, mail can even be delivered on machines inappropriately because of a le

server being down. The performance can be especially bad if you run the automounter.

The ForwardPath (J) option allows you to set a path of forward les. For example, the con-

g le line

O ForwardPath=/var/forward/$u:$z/.forward.$w

would rst look for a le with the same name as the user’s login in /var/forward; if that is not found

(or is inaccessible) the le ‘‘.forward.machinename’’ in the user’s home directory is searched. A

truly perverse site could also search by sender by using $r, $s, or $f.

If you create a directory such as /var/forward, it should be mode 1777 (that is, the sticky bit

should be set). Users should create the les mode 0644. Note that you must use the ForwardFileIn-

UnsafeDirPath and ForwardFileInUnsafeDirPathSafe ags with the DontBlameSendmail option to

allow forward les in a world writable directory. This might also be used as a denial of service

attack (users could create forward les for other users); a better approach might be to create

/var/forward mode 0755 and create empty les for each user, owned by that user, mode 0644. If

you do this, you don’t hav e to set the DontBlameSendmail options indicated above.

4.13. Free Space

On systems that have one of the system calls in the statfs(2) family (including statvfs and

ustat), you can specify a minimum number of free blocks on the queue lesystem using the Min-

FreeBlocks (b) option. If there are fewer than the indicated number of blocks free on the lesystem

on which the queue is mounted the SMTP server will reject mail with the 452 error code. This

invites the SMTP client to try again later.

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Sendmail Installation and Operation Guide

Beware of setting this option too high; it can cause rejection of email when that mail would

be processed without difculty.

4.14. Maximum Message Size

To avoid overowing your system with a large message, the MaxMessageSize option can be

set to set an absolute limit on the size of any one message. This will be advertised in the ESMTP

dialogue and checked during message collection.

4.15. Privacy Flags

The PrivacyOptions (p) option allows you to set certain ‘‘privacy’’ ags. Actually, many of

them don’t giv e you any extra privacy, rather just insisting that client SMTP servers use the HELO

command before using certain commands or adding extra headers to indicate possible spoof

attempts.

The option takes a series of ag names; the nal privacy is the inclusive or of those ags. For

example:

O PrivacyOptions=needmailhelo, noexpn

insists that the HELO or EHLO command be used before a MAIL command is accepted and dis-

ables the EXPN command.

The ags are detailed in section 5.6.

4.16. Send to Me Too

Beginning with version 8.10, sendmail includes by default the (envelope) sender in any list

expansions. For example, if “matt” sends to a list that contains “matt” as one of the members he

will get a copy of the message. If the MeToo option is set to FALSE (in the conguration le or via

the command line), this behavior is changed, i.e., the (envelope) sender is excluded in list expan-

sions.

5. THE WHOLE SCOOP ON THE CONFIGURATION FILE

This section describes the conguration le in detail.

There is one point that should be made clear immediately: the syntax of the conguration le is

designed to be reasonably easy to parse, since this is done every time sendmail starts up, rather than

easy for a human to read or write. The conguration le should be generated via the method described

in cf/README, it should not be edited directly unless someone is familiar with the internals of the

syntax described here and it is not possible to achieve the desired result via the default method.

The conguration le is organized as a series of lines, each of which begins with a single charac-

ter dening the semantics for the rest of the line. Lines beginning with a space or a tab are continuation

lines (although the semantics are not well dened in many places). Blank lines and lines beginning

with a sharp symbol (‘#’) are comments.

5.1. R and S — Rewriting Rules

The core of address parsing are the rewriting rules. These are an ordered production system.

Sendmail scans through the set of rewriting rules looking for a match on the left hand side (LHS) of

the rule. When a rule matches, the address is replaced by the right hand side (RHS) of the rule.

There are several sets of rewriting rules. Some of the rewriting sets are used internally and

must have specic semantics. Other rewriting sets do not have specically assigned semantics, and

may be referenced by the mailer denitions or by other rewriting sets.

The syntax of these two commands are:

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Sn

Sets the current ruleset being collected to n. If you begin a ruleset more than once it appends to the

old denition.

Rlhs rhs comments

The elds must be separated by at least one tab character; there may be embedded spaces in the

elds. The lhs is a pattern that is applied to the input. If it matches, the input is rewritten to the rhs.

The comments are ignored.

Macro expansions of the form $x are performed when the conguration le is read. A literal

$ can be included using $$. Expansions of the form $&x are performed at run time using a some-

what less general algorithm. This is intended only for referencing internally dened macros such as

$h that are changed at runtime.

5.1.1. The left hand side

The left hand side of rewriting rules contains a pattern. Normal words are simply

matched directly. Metasyntax is introduced using a dollar sign. The metasymbols are:

$*

Match zero or more tokens

$+

Match one or more tokens

$

Match exactly one token

$=x Match any phrase in class x

x Match any word not in class x

If any of these match, they are assigned to the symbol $n for replacement on the right hand side,

where n is the index in the LHS. For example, if the LHS:

$:$+

is applied to the input:

UCBARPA:eric

the rule will match, and the values passed to the RHS will be:

$1 UCBARPA

$2 eric

Additionally, the LHS can include $@ to match zero tokens. This is not bound to a $n on

the RHS, and is normally only used when it stands alone in order to match the null input.

5.1.2. The right hand side

When the left hand side of a rewriting rule matches, the input is deleted and replaced by

the right hand side. Tokens are copied directly from the RHS unless they begin with a dollar

sign. Metasymbols are:

$n

Substitute indenite token n from LHS

$[name$]

Canonicalize name

$(map key $@arguments $:default $)

Generalized keyed mapping function

$>n

“Call” ruleset n

$#mailer

Resolve to mailer

$@host

Specify host

$:user

Specify user

The $n syntax substitutes the corresponding value from a $+, $, $*, $=, or match on

the LHS. It may be used anywhere.

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Sendmail Installation and Operation Guide

A host name enclosed between $[ and $] is looked up in the host database(s) and replaced

by the canonical name14. For example, “$[ftp$]” might become “ftp.CS.Berkeley.EDU” and

“$[[128.32.130.2]$]” would become “vangogh.CS.Berkeley.EDU.”

Sendmail recognizes its

numeric IP address without calling the name server and replaces it with its canonical name.

The $( ... $) syntax is a more general form of lookup; it uses a named map instead of an

implicit map. If no lookup is found, the indicated default is inserted; if no default is specied

and no lookup matches, the value is left unchanged. The arguments are passed to the map for

possible use.

The $>n syntax causes the remainder of the line to be substituted as usual and then passed

as the argument to ruleset n. The nal value of ruleset n then becomes the substitution for this

rule. The $> syntax expands everything after the ruleset name to the end of the replacement

string and then passes that as the initial input to the ruleset. Recursive calls are allowed. For

example,

$>0 $>3 $1

expands $1, passes that to ruleset 3, and then passes the result of ruleset 3 to ruleset 0.

The $# syntax should only be used in ruleset zero, a subroutine of ruleset zero, or rulesets

that return decisions (e.g., check_rcpt). It causes evaluation of the ruleset to terminate immedi-

ately, and signals to sendmail that the address has completely resolved. The complete syntax for

ruleset 0 is:

$#mailer $@host $:user

This species the {mailer, host, user} 3-tuple (triple) necessary to direct the mailer. Note: the

third element ( user ) is often also called address part. If the mailer is local the host part may be

omitted15. The mailer must be a single word, but the host and user may be multi-part. If the

mailer is the built-in IPC mailer, the host may be a colon (or comma) separated list of hosts.

Each is separately MX expanded and the results are concatenated to make (essentially) one long

MX list. Hosts separated by a comma have the same MX preference, and for each colon sepa-

rated host the MX preference is increased. The user is later rewritten by the mailer-specic

envelope rewriting set and assigned to the $u macro. As a special case, if the mailer specied

has the F=@ag specied and the rst character of the $: value is “@”, the “@” is stripped off,

and a ag is set in the address descriptor that causes sendmail to not do ruleset 5 processing.

Normally, a rule that matches is retried, that is, the rule loops until it fails. A RHS may

also be preceded by a $@ or a $: to change this behavior. A $@ prex causes the ruleset to

return with the remainder of the RHS as the value. A $: prex causes the rule to terminate

immediately, but the ruleset to continue; this can be used to avoid continued application of a

rule. The prex is stripped before continuing.

The $@ and $: prexes may precede a $> spec; for example:

R$+

$: $>7 $1

matches anything, passes that to ruleset seven, and continues; the $: is necessary to avoid an

innite loop.

Substitution occurs in the order described, that is, parameters from the LHS are substi-

tuted, hostnames are canonicalized, “subroutines” are called, and nally $#, $@, and $: are pro-

cessed.

14This is actually completely equivalent to $(host hostname$). In particular, a $: default can be used.

15You may want to use it for special “per user” extensions. For example, in the address “jgm+foo@CMU.EDU”; the “+foo”

part is not part of the user name, and is passed to the local mailer for local use.

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Figure 1 - Rewriting set semantics

5.1.3. Semantics of rewriting rule sets

There are six rewriting sets that have specic semantics. Five of these are related as

depicted by gure 1.

Ruleset three should turn the address into “canonical form.” This form should have the

basic syntax:

local-part@host-domain-spec

Ruleset three is applied by sendmail before doing anything with any address.

If no “@” sign is specied, then the host-domain-spec may be appended (box “D” in Fig-

ure 1) from the sender address (if the Cag is set in the mailer denition corresponding to the

sending mailer).

Ruleset zero is applied after ruleset three to addresses that are going to actually specify

recipients. It must resolve to a {mailer, host, address} triple. The mailer must be dened in the

mailer denitions from the conguration le. The host is dened into the $h macro for use in

the argv expansion of the specied mailer. Notice: since the envelope sender address will be

used if a delivery status notication must be send, i.e., it may specify a recipient, it is also run

through ruleset zero. If ruleset zero returns a temporary error 4xy then delivery is deferred.

This can be used to temporarily disable delivery, e.g., based on the time of the day or other vary-

ing parameters. It should not be used to quarantine e-mails.

Rulesets one and two are applied to all sender and recipient addresses respectively. They

are applied before any specication in the mailer denition. They must never resolve.

Ruleset four is applied to all addresses in the message. It is typically used to translate

internal to external form.

In addition, ruleset 5 is applied to all local addresses (specically, those that resolve to a

mailer with the ‘F=5’ ag set) that do not have aliases. This allows a last minute hook for local

names.

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Sendmail Installation and Operation Guide

5.1.4. Ruleset hooks

A few extra rulesets are dened as “hooks” that can be dened to get special features.

They are all named rulesets. The “check_*” forms all give accept/reject status; falling off the

end or returning normally is an accept, and resolving to $#error is a reject or quarantine. Quar-

antining is chosen by specifying quarantine in the second part of the mailer triplet:

$#error $@ quarantine $: Reason for quarantine

Many of these can also resolve to the special mailer name $#discard; this accepts the message

as though it were successful but then discards it without delivery. Note, this mailer cannot be

chosen as a mailer in ruleset 0. Note also that all “check_*” rulesets have to deal with tempo-

rary failures, especially for map lookups, themselves, i.e., they should return a temporary error

code or at least they should make a proper decision in those cases.

5.1.4.1. check_relay

The check_relay ruleset is called after a connection is accepted by the daemon. It is

not called when sendmail is started using thebs option. It is passed

client.host.name $| client.host.address

where $| is a metacharacter separating the two parts. This ruleset can reject connections

from various locations. Note that it only checks the connecting SMTP client IP address and

hostname. It does not check for third party message relaying. The check_rcpt ruleset dis-

cussed below usually does third party message relay checking.

5.1.4.2. check_mail

The check_mail ruleset is passed the user name parameter of the SMTP MAIL com-

mand. It can accept or reject the address.

5.1.4.3. check_rcpt

The check_rcpt ruleset is passed the user name parameter of the SMTP RCPT com-

mand. It can accept or reject the address.

5.1.4.4. check_data

The check_data ruleset is called after the SMTP DAT A command, its parameter is the

number of recipients. It can accept or reject the command.

5.1.4.5. check_other

The check_other ruleset is invoked for all unknown SMTP commands and for com-

mands which do not have specic rulesets, e.g., NOOP and VERB. Internal checks, e.g.,

those explained in "Measures against Denial of Service Attacks", are performed rst. The

ruleset is passed

entire-SMTP-command $| SMTP-reply-rst-digit

where $| is a metacharacter separating the two parts. For example,

VERB $| 2

reects receiving the "VERB" SMTP command and the intent to return a "2XX" SMTP suc-

cess reply. Alternatively,

JUNK TYPE=I $| 5

reects receiving the unknown "JUNK TYPE=I" SMTP command and the intent to return a

"5XX" SMTP failure reply. If the ruleset returns the SMTP reply code 421:

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$#error $@ 4.7.0 $: 421 bad command

the session is terminated. Note: it is a bad idea to return the original command in the error

text to the client as that might be abused for certain attacks. The ruleset cannot override a

rejection triggered by the built-in rules.

5.1.4.6. check_compat

The check_compat ruleset is passed

sender-address $| recipient-address

where $| is a metacharacter separating the addresses. It can accept or reject mail transfer

between these two addresses much like the checkcompat() function. Note: while other

check_* rulesets are invoked during the SMTP mail receiption stage (i.e., in the SMTP

server), check_compat is invoked during the mail delivery stage.

5.1.4.7. check_eoh

The check_eoh ruleset is passed

number-of-headers $| size-of-headers

where $| is a metacharacter separating the numbers. These numbers can be used for size

comparisons with the arith map. The ruleset is triggered after all of the headers have been

read. It can be used to correlate information gathered from those headers using the macro

storage map. One possible use is to check for a missing header. For example:

Kstorage macro

HMessage-Id: $>CheckMessageId

SCheckMessageId

# Record the presence of the header

R$*

$: $(storage {MessageIdCheck} $@ OK $) $1

R< $+ @ $+ >

$@ OK

R$*

$#error $: 553 Header Error

Scheck_eoh

# Check the macro

R$*

$: < $&{MessageIdCheck} >

# Clear the macro for the next message

R$*

$: $(storage {MessageIdCheck} $) $1

# Has a Message-Id: header

R< $+ >

$@ OK

# Allow missing Message-Id: from local mail

R$*

$: < $&{client_name} >

R< >

$@ OK

R< $=w >

$@ OK

# Otherwise, reject the mail

R$*

$#error $: 553 Header Error

Keep in mind the Message-Id: header is not a required header and is not a guaranteed spam

indicator. This ruleset is an example and should probably not be used in production.

5.1.4.8. check_eom

The check_eom ruleset is called after the end of a message, its parameter is the mes-

sage size. It can accept or reject the message.

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Sendmail Installation and Operation Guide

5.1.4.9. check_etrn

The check_etrn ruleset is passed the parameter of the SMTP ETRN command. It can

accept or reject the command.

5.1.4.10. check_expn

The check_expn ruleset is passed the user name parameter of the SMTP EXPN com-

mand. It can accept or reject the address.

5.1.4.11. check_vrfy

The check_vrfy ruleset is passed the user name parameter of the SMTP VRFY com-

mand. It can accept or reject the command.

5.1.4.12. clt_features

The clt_features ruleset is called with the server’s host name before sendmail connects

to it (only if sendmail is compiled with STARTTLS or SASL). This ruleset should return $#

followed by a list of options (in general, single characters delimited by white space). If the

return value starts with anything else it is silently ignored. Generally upper case characters

turn off a feature while lower case characters turn it on. Options ‘D’/‘M’ cause the client to

not use DANE/MTA-STS, respectively, which is useful to interact with MTAs that have bro-

ken DANE/MTA-STS setups by simply not using it. Note: The d option in tls_clt_features

to turn off DANE does not work when the server does not even offer STARTTLS.

5.1.4.13. trust_auth

The trust_auth ruleset is passed the AUTH= parameter of the SMTP MAIL command.

It is used to determine whether this value should be trusted. In order to make this decision,

the ruleset may make use of the various ${auth_*} macros. If the ruleset does resolve to the

“error” mailer the AUTH= parameter is not trusted and hence not passed on to the next relay.

5.1.4.14. tls_client

The tls_client ruleset is called when sendmail acts as server: after a STARTTLS com-

mand has been issued and the TLS handshake was performed, and from check_mail. The

parameter is the value of ${verify} and STARTTLS or MAIL, respectively. If the ruleset

does resolve to the “error” mailer, the appropriate error code is returned to the client, for

STARTTLS this happens for (most) subsequent commands.

5.1.4.15. tls_server

The tls_server ruleset is called when sendmail acts as client after a STARTTLS com-

mand (should) have been issued. The parameter is the value of ${verify}. If the ruleset does

resolve to the “error” mailer, the connection is aborted (treated as non-deliverable with a per-

manent or temporary error).

5.1.4.16. tls_rcpt

The tls_rcpt ruleset is called each time before a RCPT command is sent. The parame-

ter is the current recipient. If the ruleset does resolve to the “error” mailer, the RCPT com-

mand is suppressed (treated as non-deliverable with a permanent or temporary error). This

ruleset allows to require encryption or verication of the recipient’s MTA even if the mail is

somehow redirected to another host. For example, sending mail to luke@endmail.org may

get redirected to a host named death.star and hence the tls_server ruleset won’t apply. By

introducing per recipient restrictions such attacks (e.g., via DNS spoong) can be made

impossible. See cf/README how this ruleset can be used.

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SMM:08-45

5.1.4.17. srv_features

The srv_features ruleset is called with the connecting client’s host name when a client

connects to sendmail. This ruleset should return $# followed by a list of options (in general,

single characters delimited by white space). If the return value starts with anything else it is

silently ignored. Generally upper case characters turn off a feature while lower case charac-

ters turn it on. Option ‘S’ causes the server not to offer STARTTLS, which is useful to inter-

act with MTAs/MUAs that have broken STARTTLS implementations by simply not offering

it. ‘V’ turns off the request for a client certicate during the TLS handshake. Options ‘A’

and ‘P’ suppress SMTP AUTH and PIPELINING, respectively. ‘c’ is the equivalent to

AuthOptions=p, i.e., it doesn’t permit mechanisms susceptible to simple passive attack (e.g.,

PLAIN, LOGIN), unless a security layer is active. Option ‘l’ requires SMTP AUTH for a

connection. Options ’B’, ’D’, ’E’, and ’X’ suppress SMTP VERB, DSN, ETRN, and

EXPN, respectively. If a client sends one of the (HTTP) commands GET, POST, CON-

NECT, or USER the connection is immediately terminated in the following cases: if sent as

rst command, if sent as rst command after STARTTLS, or if the ’h’ option is set. Option

’F’ disables SMTP transaction stufng protection which is enabled by default. The protec-

tion checks for clients which try to send commands without waiting for the server

HELO/EHLO and DAT A response. Option ’o’ causes the server to accept only CRLF .

CRLF as end of an SMTP message as required by the RFCs which is also a defense against

SMTP smuggling (CVE-2023-51765). Option ’O’ allows the server to accept a single dot

on a line by itself as end of an SMTP message. Option ’g’ instructs the server to fail SMTP

messages which have a LF without a CR directly before it ("bare LF") by dropping the ses-

sion with a 421 error. Option ’G’ accepts SMTP messages which have a "bare LF". Option

’u’ instructs the server to fail SMTP messages which have a CR without a LF directly after it

("bare CR") by dropping the session with a 421 error. Option ’U’ accepts SMTP messages

which have a "bare CR". There is a variant for the options ’u’ and ’g’: a ’2’ can be

appended to the single character, in which case the server will replace the offending bare CR

or bare LF with a space. This allows to accept mail from broken systems, but the message is

modied to avoid SMTP smuggling. If needed, systems with broken SMTP implementa-

tions can be allowed some violations, e.g., a combination of

G U g2 u2 O

A command like

egrep ’Bare.*(CR|LF).*not allowed’ $MAILLOG

can be used to nd hosts which send bare CR or LF.

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Sendmail Installation and Operation Guide

A

Do not offer AUTH

a

Offer AUTH (default)

B

Do not offer VERB

b

Offer VERB (default)

C

Do not require security layer for

plaintext AUTH (default)

c

Require security layer for plaintext AUTH

D

Do not offer DSN

d

Offer DSN (default)

E

Do not offer ETRN

e

Offer ETRN (default)

F

Disable transaction stufng protection

f

Enforce transaction stufng protection (default)

G

Accept "bare LF"s in a message

g

Do not accept "bare LF"s in a message (default)

g2

Replace "bare LF" in a message with space

h

Terminate session after HTTP commands

L

Do not require AUTH (default)

l

Require AUTH

O

Accept a single dot on a line by itself

as end of an SMTP message

o

Require CRLF . CRLF as end of an SMTP message (default)

P

Do not offer PIPELINING

p

Offer PIPELINING (default)

S

Do not offer STARTTLS

s

Offer STARTTLS (default)

U

Accept "bare CR"s in a message

u

Do not accept "bare CR"s in a message (default)

u2

Replace "bare CR" in a message with space

V

Do not request a client certicate

v

Request a client certicate (default)

X

Do not offer EXPN

x

Offer EXPN (default)

Note: the entries marked as ‘‘(default)’’ may require that some conguration has been made,

e.g., SMTP AUTH is only available if properly congured. Moreover, many options can be

changed on a global basis via other settings as explained in this document, e.g., via Daemon-

PortOptions.

The ruleset may return ‘$#temp’ to indicate that there is a temporary problem deter-

mining the correct features, e.g., if a map is unavailable. In that case, the SMTP server

issues a temporary failure and does not accept email.

5.1.4.18. try_tls

The try_tls ruleset is called when sendmail connects to another MTA. The argument

for the ruleset is the name of the server. If the ruleset does resolve to the “error” mailer,

sendmail does not try STARTTLS even if it is offered. This is useful to deal with START-

TLS interoperability issues by simply not using it.

5.1.4.19. tls_srv_features and tls_clt_features

The tls_clt_features ruleset is called right before sendmail issues the STARTTLS com-

mand to another MTA and the tls_srv_features ruleset is called when a client sends the

STARTTLS command to sendmail. The arguments for the rulesets are the host name and IP

address of the other side separated by $| (which is a metacharacter). They should return a

Sendmail Installation and Operation Guide

SMM:08-47

list of key=value pairs separated by semicolons; the list can be empty if no options should be

applied to the connection. Av ailable keys are and their allowed values are:

Options

A comma separated list of SSL related options. See ServerSSLOptions and ClientSS-

LOptions for details, as well as SSL_set_options(3) and note this warning: Options

already set before are not cleared!

CipherList

Specify cipher list for STARTTLS (does not apply to TLSv1.3), see ciphers(1) for possi-

ble values. This overrides the global CipherList for the session.

CertFile

File containing a certicate.

Ke yFile

File containing the private key for the certicate.

Flags

Currently the only valid ags are

R to require a CRL for each encountered certicate during verication (by default a

missing CRL is ignored),

c and C which basically clears/sets the option TLSFallbacktoClear for just this session,

respectively,

d to turn off DANE which is obviously only valid for tls_clt_features and requires DANE

to be compiled in. This might be needed in case of a misconguration, e.g., specifying

invalid TLSA RRs.

Example:

Stls_srv_features

R$* $| 10.$+

$: cipherlist=HIGH

Notes:

Errors in these features (e.g., unknown keys or inv alid values) are logged and the cur-

rent session is aborted to avoid using STARTTLS with features that should have been

changed.

The keys are case-insensitive.

Both CertFile and Ke yFile must be specied together; specifying only one is an error.

5.1.4.20. authinfo

The authinfo ruleset is called when sendmail tries to authenticate to another MTA.

The arguments for the ruleset are the host name and IP address of the server separated by $|

(which is a metacharacter). It should return $# followed by a list of tokens that are used for

SMTP AUTH. If the return value starts with anything else it is silently ignored. Each token

is a tagged string of the form: "TDstring" (including the quotes), where

T

Tag which describes the item

D

Delimiter: ’:’ simple text follows

’=’ string is base64 encoded

string

Value of the item

Valid values for the tag are:

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Sendmail Installation and Operation Guide

U

user (authorization) id

I

authentication id

P

password

R

realm

M

list of mechanisms delimited by spaces

If this ruleset is dened, the option DefaultAuthInfo is ignored (even if the ruleset does not

return a ‘‘useful’’ result).

5.1.4.21. queuegroup

The queuegroup ruleset is used to map a recipient address to a queue group name.

The input for the ruleset is the recipient address (i.e., the address part of the resolved triple)

The ruleset should return $# followed by the name of a queue group. If the return value

starts with anything else it is silently ignored. See the section about ‘‘Queue Groups and

Queue Directories’’ for further information.

5.1.4.22. greet_pause

The greet_pause ruleset is used to specify the amount of time to pause before sending

the initial SMTP 220 greeting. The arguments for the ruleset are the host name and IP

address of the client separated by $| (which is a metacharacter). If any trafc is received

during that pause, an SMTP 554 rejection response is given instead of the 220 greeting and

all SMTP commands are rejected during that connection. This helps protect sites from open

proxies and SMTP slammers. The ruleset should return $# followed by the number of mil-

liseconds (thousandths of a second) to pause. If the return value starts with anything else or

is not a number, it is silently ignored. Note: this ruleset is not invoked (and hence the feature

is disabled) when smtps (SMTP over SSL) is used, i.e., the s modier is set for the daemon

via DaemonPortOptions, because in this case the SSL handshake is performed before the

greeting is sent.

5.1.5. IPC mailers

Some special processing occurs if the ruleset zero resolves to an IPC mailer (that is, a

mailer that has “[IPC]” listed as the Path in the M conguration line. The host name passed

after “$@” has MX expansion performed if not delivering via a named socket; this looks the

name up in DNS to nd alternate delivery sites.

The host name can also be provided as a dotted quad or an IPv6 address in square brack-

ets; for example:

[128.32.149.78]

or

[IPv6:2002:c0a8:51d2::23f4]

This causes direct conversion of the numeric value to an IP host address.

The host name passed in after the “$@” may also be a colon or comma separated list of

hosts. Each is separately MX expanded and the results are concatenated to make (essentially)

one long MX list. Hosts separated by a comma have the same MX preference, and for each

colon separated host the MX preference is increased. The intent here is to create “fake” MX

records that are not published in DNS for private internal networks.

As a nal special case, the host name can be passed in as a text string in square brackets:

[ucbvax.berkeley.edu]

This form avoids the MX mapping. N.B.: This is intended only for situations where you have a

network rewall or other host that will do special processing for all your mail, so that your MX

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record points to a gateway machine; this machine could then do direct delivery to machines

within your local domain. Use of this feature directly violates RFC 1123 section 5.3.5: it should

not be used lightly.

5.2. D — Dene Macro

Macros are named with a single character or with a word in {braces}. The names ‘‘x’’ and

‘‘{x}’’ denote the same macro for every single character ‘‘x’’. Single character names may be

selected from the entire ASCII set, but user-dened macros should be selected from the set of upper

case letters only. Lower case letters and special symbols are used internally. Long names beginning

with a lower case letter or a punctuation character are reserved for use by sendmail, so user-dened

long macro names should begin with an upper case letter.

The syntax for macro denitions is:

Dx val

where x is the name of the macro (which may be a single character or a word in braces) and val is

the value it should have. There should be no spaces given that do not actually belong in the macro

value.

Macros are interpolated using the construct $x, where x is the name of the macro to be inter-

polated. This interpolation is done when the conguration le is read, except in M lines. The spe-

cial construct $&x can be used in R lines to get deferred interpolation.

Conditionals can be specied using the syntax:

$?x text1 $| text2 $.

This interpolates text1 if the macro $x is set and non-null, and text2 otherwise. The “else” ($|)

clause may be omitted.

The following macros are dened and/or used internally by sendmail for interpolation into

argv’s for mailers or for other contexts. The ones marked † are information passed into sendmail16,

the ones marked ‡ are information passed both in and out of sendmail, and the unmarked macros are

passed out of sendmail but are not otherwise used internally. These macros are:

$a

The origination date in RFC 822 format. This is extracted from the Date: line.

$b

The current date in RFC 822 format.

$c

The hop count. This is a count of the number of Received: lines plus the value of theh com-

mand line ag.

$d

The current date in UNIX (ctime) format.

$e†

(Obsolete; use SmtpGreetingMessage option instead.) The SMTP entry message. This is

printed out when SMTP starts up. The rst word must be the $j macro as specied by RFC

821. Defaults to “$j Sendmail $v ready at $b”. Commonly redened to include the congu-

ration version number, e.g., “$j Sendmail $v/$Z ready at $b”

$f

The envelope sender (from) address.

$g

The sender address relative to the recipient. For example, if $f is “foo”, $g will be “host!foo”,

“foo@host.domain”, or whatever is appropriate for the receiving mailer.

$h

The recipient host. This is set in ruleset 0 from the $@ eld of a parsed address.

$i

The queue id, e.g., “f344MXxp018717”.

16As of version 8.6, all of these macros have reasonable defaults. Previous versions required that they be dened.

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Sendmail Installation and Operation Guide

$j‡

The “ofcial” domain name for this site. This is fully qualied if the full qualication can be

found. It must be redened to be the fully qualied domain name if your system is not con-

gured so that information can nd it automatically.

$k

The UUCP node name (from the uname system call).

$l†

(Obsolete; use UnixFromLine option instead.) The format of the UNIX from line. Unless

you have changed the UNIX mailbox format, you should not change the default, which is

“From $g $d”.

$m

The domain part of the gethostname return value. Under normal circumstances, $j is equiv-

alent to $w.$m.

$n† The name of the daemon (for error messages). Defaults to “MAILER-DAEMON”.

$o† (Obsolete: use OperatorChars option instead.) The set of “operators” in addresses. A list of

characters which will be considered tokens and which will separate tokens when doing pars-

ing. For example, if “@” were in the $o macro, then the input “a@b” would be scanned as

three tokens: “a,” “@,” and “b.” Defaults to “.:@[]”, which is the minimum set necessary to

do RFC 822 parsing; a richer set of operators is “.:%@!/[]”, which adds support for UUCP,

the %-hack, and X.400 addresses.

$p

Sendmail’s process id.

$r

Protocol used to receive the message. Set from thep command line ag or by the SMTP

server code.

$s

Sender’s host name. Set from thep command line ag or by the SMTP server code (in

which case it is set to the EHLO/HELO parameter).

$t

A numeric representation of the current time in the format YYYYMMDDHHmm (4 digit

year 1900-9999, 2 digit month 01-12, 2 digit day 01-31, 2 digit hours 00-23, 2 digit minutes

00-59).

$u

The recipient user.

$v

The version number of the sendmail binary.

$w‡ The hostname of this site. This is the root name of this host (but see below for caveats).

$x

The full name of the sender.

$z

The home directory of the recipient.

$_

The validated sender address. See also ${client_resolve}.

${addr_type}

The type of the address which is currently being rewritten. This macro contains up to three

characters, the rst is either ‘e’ or ‘h’ for envelope/header address, the second is a space, and

the third is either ‘s’ or ‘r’ for sender/recipient address.

${alg_bits}

The maximum keylength (in bits) of the symmetric encryption algorithm used for a TLS con-

nection. This may be less than the effective keylength, which is stored in ${cipher_bits}, for

‘‘export controlled’’ algorithms.

${auth_authen}

The client’s authentication credentials as determined by authentication (only set if success-

ful). The format depends on the mechanism used, it might be just ‘user’, or ‘user@realm’, or

something similar (SMTP AUTH only).

${auth_author}

The authorization identity, i.e. the AUTH= parameter of the SMTP MAIL command if sup-

plied.

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SMM:08-51

${auth_type}

The mechanism used for SMTP authentication (only set if successful).

${auth_ssf}

The keylength (in bits) of the symmetric encryption algorithm used for the security layer of a

SASL mechanism.

${bodytype}

The message body type (7BIT or 8BITMIME), as determined from the envelope.

${cert_fp}

The ngerprint of the presented certicate (STARTTLS only). Note: this macro is only

dened if the option CertFingerprintAlgorithm is set, in which case the specied ngerprint

algorithm is used. The valid algorithms depend on the OpenSSL version, but usually md5,

sha1, and sha256 are available. See

openssl dgst -h

for a list.

${cert_issuer}

The DN (distinguished name) of the CA (certicate authority) that signed the presented cer-

ticate (the cert issuer) (STARTTLS only).

${cert_md5}

The MD5 hash of the presented certicate (STARTTLS only). Note: this macro is only

dened if the option CertFingerprintAlgorithm is not set.

${cert_subject}

The DN of the presented certicate (called the cert subject) (STARTTLS only).

${cipher}

The cipher suite used for the connection, e.g., EDH-DSS-DES-CBC3-SHA, EDH-RSA-DES-

CBC-SHA, DES-CBC-MD5, DES-CBC3-SHA (STARTTLS only).

${cipher_bits}

The effective keylength (in bits) of the symmetric encryption algorithm used for a TLS con-

nection.

${client_addr}

The IP address of the SMTP client. IPv6 addresses are tagged with "IPv6:" before the

address. Dened in the SMTP server only.

${client_connections}

The number of open connections in the SMTP server for the client IP address.

${client_ags}

The ags specied by the Modier= part of ClientPortOptions where ags are separated

from each other by spaces and upper case ags are doubled. That is, Modier=hA will be

represented as "h AA" in ${client_ags}, which is required for testing the ags in rulesets.

${client_name}

The host name of the SMTP client. This may be the client’s bracketed IP address in the form

[ nnn.nnn.nnn.nnn ] for IPv4 and [ IPv6:nnnn:...:nnnn ] for IPv6 if the client’s IP address is

not resolvable, or if it is resolvable but the IP address of the resolved hostname doesn’t match

the original IP address. Dened in the SMTP server only. See also ${client_resolve}.

${client_port}

The port number of the SMTP client. Dened in the SMTP server only.

${client_ptr}

The result of the PTR lookup for the client IP address.

Note: this is the same as

${client_name} if and only if ${client_resolve} is OK. Dened in the SMTP server only.

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${client_rate}

The number of incoming connections for the client IP address over the time interval specied

by ConnectionRateWindowSize.

${client_resolve}

Holds the result of the resolve call for ${client_name}. Possible values are:

OK

resolved successfully

FAIL

permanent lookup failure

FORGED forward lookup doesn’t match reverse lookup

TEMP

temporary lookup failure

Dened in the SMTP server only. sendmail performs a hostname lookup on the IP address of

the connecting client. Next the IP addresses of that hostname are looked up. If the client IP

address does not appear in that list, then the hostname is maybe forged. This is reected as

the value FORGED for ${client_resolve} and it also shows up in $_ as "(may be forged)".

${cn_issuer}

The CN (common name) of the CA that signed the presented certicate (STARTTLS only).

Note: if the CN cannot be extracted properly it will be replaced by one of these strings based

on the encountered error:

BadCerticateContainsNUL

CN contains a NUL character

BadCerticateTooLong

CN is too long

BadCerticateUnknown

CN could not be extracted

In the last case, some other (unspecic) error occurred.

${cn_subject}

The CN (common name) of the presented certicate (STARTTLS only). See ${cn_issuer}

for possible replacements.

${currHeader}

Header value as quoted string (possibly truncated to MAXNAME). This macro is only avail-

able in header check rulesets.

${daemon_addr}

The IP address the daemon is listening on for connections.

${daemon_family}

The network family if the daemon is accepting network connections. Possible values include

“inet”, “inet6”, “iso”, “ns”, “x.25”

${daemon_ags}

The ags for the daemon as specied by the Modier= part of DaemonPortOptions whereby

the ags are separated from each other by spaces, and upper case ags are doubled. That is,

Modier=Ea will be represented as "EE a" in ${daemon_ags}, which is required for testing

the ags in rulesets.

${daemon_info}

Some information about a daemon as a text string.

For example, “SMTP+queue-

ing@00:30:00”.

${daemon_name}

The name of the daemon from DaemonPortOptions Name= suboption. If this suboption is

not set, "Daemon#", where # is the daemon number, is used.

${daemon_port}

The port the daemon is accepting connection on. Unless DaemonPortOptions is set, this

will most likely be “25”.

${deliveryMode}

The current delivery mode sendmail is using.

It is initially set to the value of the

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SMM:08-53

DeliveryMode option.

${dsn_envid}

The envelope id parameter (ENVID=) passed to sendmail as part of the envelope.

${dsn_notify}

Value of DSN NOTIFY= parameter (never, success, failure, delay, or empty string).

${dsn_ret}

Value of DSN RET= parameter (hdrs, full, or empty string).

${envid}

The envelope id parameter (ENVID=) passed to sendmail as part of the envelope.

${hdrlen}

The length of the header value which is stored in ${currHeader} (before possible truncation).

If this value is greater than or equal to MAXNAME the header has been truncated.

${hdr_name}

The name of the header eld for which the current header check ruleset has been called. This

is useful for a default header check ruleset to get the name of the header; the macro is only

available in header check rulesets.

${if_addr}

The IP address of the interface of an incoming connection unless it is in the loopback net.

IPv6 addresses are tagged with "IPv6:" before the address.

${if_addr_out}

The IP address of the interface of an outgoing connection unless it is in the loopback net.

IPv6 addresses are tagged with "IPv6:" before the address.

${if_family}

The IP family of the interface of an incoming connection unless it is in the loopback net.

${if_family_out}

The IP family of the interface of an outgoing connection unless it is in the loopback net.

${if_name}

The hostname associated with the interface of an incoming connection. This macro can be

used for SmtpGreetingMessage and HReceived for virtual hosting. For example:

O SmtpGreetingMessage=$?{if_name}${if_name}$|$j$. MTA

${if_name_out}

The name of the interface of an outgoing connection.

${load_avg}

The current load average.

${mail_addr}

The address part of the resolved triple of the address given for the SMTP MAIL command.

Dened in the SMTP server only.

${mail_host}

The host from the resolved triple of the address given for the SMTP MAIL command. Dened

in the SMTP server only.

${mail_mailer}

The mailer from the resolved triple of the address given for the SMTP MAIL command.

Dened in the SMTP server only.

${msg_id}

The value of the Message-Id: header.

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Sendmail Installation and Operation Guide

${msg_size}

The value of the SIZE= parameter, i.e., usually the size of the message (in an ESMTP dia-

logue), before the message has been collected, thereafter the message size as computed by

sendmail (and can be used in check_compat).

${nbadrcpts}

The number of bad recipients for a single message.

${nrcpts}

The number of validated recipients for a single message. Note: since recipient validation hap-

pens after check_rcpt has been called, the value in this ruleset is one less than what might be

expected.

${ntries}

The number of delivery attempts.

${opMode}

The current operation mode (from thebag).

${quarantine}

The quarantine reason for the envelope, if it is quarantined.

${queue_interval}

The queue run interval given by theqag. For example,q30m would set ${queue_inter-

val} to “00:30:00”.

${rcpt_addr}

The address part of the resolved triple of the address given for the SMTP RCPT command.

Dened in the SMTP server only after a RCPT command.

${rcpt_host}

The host from the resolved triple of the address given for the SMTP RCPT command. Dened

in the SMTP server only after a RCPT command.

${rcpt_mailer}

The mailer from the resolved triple of the address given for the SMTP RCPT command.

Dened in the SMTP server only after a RCPT command.

${server_addr}

The address of the server of the current outgoing SMTP connection. For LMTP delivery the

macro is set to the name of the mailer. (only if sendmail is compiled with STARTTLS or

SASL.)

${server_name}

The name of the server of the current outgoing SMTP or LMTP connection. (only if send-

mail is compiled with STARTTLS or SASL.)

${time}

The output of the time(3) function, i.e., the number of seconds since 0 hours, 0 minutes, 0 sec-

onds, January 1, 1970, Coordinated Universal Time (UTC).

${tls_version}

The TLS/SSL version used for the connection, e.g., TLSv1.2, TLSv1; dened after START-

TLS has been used.

${total_rate}

The total number of incoming connections over the time interval specied by Connection-

RateWindowSize.

${verify}

The result of the verication of the presented cert; only dened after STARTTLS has been

used (or attempted). Possible values are:

Sendmail Installation and Operation Guide

SMM:08-55

TRUSTED

verication via DANE succeeded.

DANE_FAIL

verication via DANE failed.

DANE_TEMP verication via DANE failed temporarily.

DANE_NOTLS DANE required but STARTTLS was not available.

OK

verication succeeded.

NO

no cert presented.

NOT

no cert requested.

FAIL

cert presented but could not be veried,

e.g., the signing CA is missing.

NONE

STARTTLS has not been performed.

CLEAR

STARTTLS has been disabled internally

for a clear text delivery attempt.

TEMP

temporary error occurred.

PROT OCOL

some protocol error occurred

at the ESMTP level (not TLS).

CONFIG

tls_*_features failed due to a syntax error.

SOFTWARE

STARTTLS handshake failed,

which is a fatal error for this session,

the e-mail will be queued.

There are three types of dates that can be used. The $a and $b macros are in RFC 822 for-

mat; $a is the time as extracted from the “Date:” line of the message (if there was one), and $b is

the current date and time (used for postmarks). If no “Date:” line is found in the incoming message,

$a is set to the current time also. The $d macro is equivalent to the $b macro in UNIX (ctime) for-

mat.

The macros $w, $j, and $m are set to the identity of this host. Sendmail tries to nd the fully

qualied name of the host if at all possible; it does this by calling gethostname(2) to get the current

hostname and then passing that to gethostbyname(3) which is supposed to return the canonical ver-

sion of that host name.17 Assuming this is successful, $j is set to the fully qualied name and $m is

set to the domain part of the name (everything after the rst dot). The $w macro is set to the rst

word (everything before the rst dot) if you have a lev el 5 or higher conguration le; otherwise, it

is set to the same value as $j. If the canonication is not successful, it is imperative that the cong

le set $j to the fully qualied domain name18.

The $f macro is the id of the sender as originally determined; when mailing to a specic host

the $g macro is set to the address of the sender relative to the recipient. For example, if I send to

“bollard@matisse.CS.Berkeley.EDU” from the machine “vangogh.CS.Berkeley.EDU” the $f macro

will be “eric” and the $g macro will be “eric@vangogh.CS.Berkeley.EDU.”

The $x macro is set to the full name of the sender. This can be determined in several ways. It

can be passed as ag to sendmail. It can be dened in the NAME environment variable. The third

choice is the value of the “Full-Name:” line in the header if it exists, and the fourth choice is the

comment eld of a “From:” line. If all of these fail, and if the message is being originated locally,

the full name is looked up in the /etc/passwdle.

When sending, the $h, $u, and $z macros get set to the host, user, and home directory (if

local) of the recipient. The rst two are set from the $@ and $: part of the rewriting rules, respec-

tively.

17For example, on some systems gethostname might return “foo” which would be mapped to “foo.bar.com” by gethostbyname.

18Older versions of sendmail didn’t pre-dene $j at all, so up until 8.6, cong les always had to dene $j.

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Sendmail Installation and Operation Guide

The $p and $t macros are used to create unique strings (e.g., for the “Message-Id:” eld).

The $i macro is set to the queue id on this host; if put into the timestamp line it can be extremely

useful for tracking messages. The $v macro is set to be the version number of sendmail; this is nor-

mally put in timestamps and has been proven extremely useful for debugging.

The $celd is set to the “hop count,” i.e., the number of times this message has been pro-

cessed. This can be determined by thehag on the command line or by counting the timestamps

in the message.

The $r and $selds are set to the protocol used to communicate with sendmail and the send-

ing hostname. They can be set together using thep command line ag or separately using theM

oroMags.

The $_ is set to a validated sender host name. If the sender is running an RFC 1413 compli-

ant IDENT server and the receiver has the IDENT protocol turned on, it will include the user name

on that host.

The ${client_name}, ${client_addr}, and ${client_port} macros are set to the name,

address, and port number of the SMTP client who is invoking sendmail as a server. These can be

used in the check_* rulesets (using the $& deferred evaluation form, of course!).

5.3. C and F — Dene Classes

Classes of phrases may be dened to match on the left hand side of rewriting rules, where a

“phrase” is a sequence of characters that does not contain space characters. For example a class of

all local names for this site might be created so that attempts to send to oneself can be eliminated.

These can either be dened directly in the conguration le or read in from another le. Classes are

named as a single letter or a word in {braces}. Class names beginning with lower case letters and

special characters are reserved for system use. Classes dened in cong les may be given names

from the set of upper case letters for short names or beginning with an upper case letter for long

names.

The syntax is:

Cc phrase1 phrase2...

Fcle

Fc |program

Fc [mapkey]@mapclass:mapspec

The rst form denes the class c to match any of the named words. If phrase1 or phrase2 is another

class, e.g., $=S, the contents of class S are added to class c. It is permissible to split them among

multiple lines; for example, the two forms:

CHmonet ucbmonet

and

CHmonet

CHucbmonet

are equivalent. The ‘‘F’’ forms read the elements of the class c from the namedle, program, or

map specication. Each element should be listed on a separate line. To specify an optional le, use

‘‘o’’ between the class name and the le name, e.g.,

Fc o /path/to/le

If the le can’t be used, sendmail will not complain but silently ignore it. The map form should be

an optional map key, an at sign, and a map class followed by the specication for that map. Exam-

ples include:

F{VirtHosts}@ldap:k (&(objectClass=virtHosts)(host=*)) v host

F{MyClass}foo@hash:/etc/mail/classes

Sendmail Installation and Operation Guide

SMM:08-57

will ll the class $={VirtHosts} from an LDAP map lookup and $={MyClass} from a hash

database map lookup of the key foo. There is also a built-in schema that can be accessed by only

specifying:

F{ClassName}@LDAP

This will tell sendmail to use the default schema:

k (&(objectClass=sendmailMTAClass)

(sendmailMTAClassName=ClassName)

(|(sendmailMTACluster=${sendmailMTACluster})

(sendmailMTAHost=$j)))

v sendmailMTAClassValue

Note that the lookup is only done when sendmail is initially started.

Elements of classes can be accessed in rules using $= or. The (match entries not in

class) only matches a single word; multi-word entries in the class are ignored in this context.

Some classes have internal meaning to sendmail:

$=e

contains the Content-Transfer-Encodings that can be 87 bit encoded. It is predened to

contain “7bit”, “8bit”, and “binary”.

$=k

set to be the same as $k, that is, the UUCP node name.

$=m

set to the set of domains by which this host is known, initially just $m.

$=n

can be set to the set of MIME body types that can never be eight to seven bit encoded. It

defaults to “multipart/signed”. Message types “message/*” and “multipart/*” are never

encoded directly. Multipart messages are always handled recursively. The handling of

message/* messages are controlled by class $=s.

$=q

A set of Content-Types that will never be encoded as base64 (if they hav e to be encoded,

they will be encoded as quoted-printable). It can have primary types (e.g., “text”) or full

types (such as “text/plain”).

$=s

contains the set of subtypes of message that can be treated recursively. By default it con-

tains only “rfc822”. Other “message/*” types cannot be 87 bit encoded. If a message

containing eight bit data is sent to a seven bit host, and that message cannot be encoded

into seven bits, it will be stripped to 7 bits.

$=t

set to the set of trusted users by the T conguration line. If you want to read trusted users

from a le, use Ft/le/name.

$=w

set to be the set of all names this host is known by. This can be used to match local host-

names.

$={persistentMacros}

set to the macros that should be saved across queue runs. Care should be taken when

adding macro names to this class.

Sendmail can be compiled to allow a scanf(3) string on the F line. This lets you do simplistic

parsing of text les. For example, to read all the user names in your system /etc/passwdle into a

class, use

FL/etc/passwd %[ˆ:]

which reads every line up to the rst colon.

5.4. E — Set or Propagate Environment Variables

E conguration lines set or propagate environment variables into children.

Ename

will propagate the named variable from the environment when sendmail was inv oked into any

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Sendmail Installation and Operation Guide

children it calls;

Ename=value

sets the named variable to the indicated value. Any variables not explicitly named will not be in the

child environment.

5.5. M — Dene Mailer

Programs and interfaces to mailers are dened in this line. The format is:

Mname, {eld=value }*

where name is the name of the mailer (used internally only) and the “eld=name” pairs dene

attributes of the mailer. Fields are:

Path

The pathname of the mailer

Flags

Specialags for this mailer

Sender

Rewriting set(s) for sender addresses

Recipient

Rewriting set(s) for recipient addresses

recipients

Maximum number of recipients per envelope

Argv

An argument vector to pass to this mailer

Eol

The end-of-line string for this mailer

Maxsize

The maximum message length to this mailer

maxmessages

The maximum message deliveries per connection

Linelimit

The maximum line length in the message body

Directory

The working directory for the mailer

Userid

The default user and group id to run as

Nice

The nice(2) increment for the mailer

Charset

The default character set for 8-bit characters

Type

Type information for DSN diagnostics

Wait

The maximum time to wait for the mailer

Queuegroup

The default queue group for the mailer

/

The root directory for the mailer

Only the rst character of the eld name is checked (it’s case-sensitive).

The following ags may be set in the mailer description. Any other ags may be used freely

to conditionally assign headers to messages destined for particular mailers. Flags marked with † are

not interpreted by the sendmail binary; these are the conventionally used to correlate to the ags

portion of the H line. Flags marked with ‡ apply to the mailers for the sender address rather than

the usual recipient mailers.

a

Run Extended SMTP (ESMTP) protocol (dened in RFCs 1869, 1652, and 1870). This ag

defaults on if the SMTP greeting message includes the word “ESMTP”.

A

Look up the user (address) part of the resolved mailer triple, in the alias database. Normally

this is only set for local mailers.

b

Force a blank line on the end of a message. This is intended to work around some stupid ver-

sions of /bin/mail that require a blank line, but do not provide it themselves. It would not nor-

mally be used on network mail.

B

Strip leading backslashes (\) off of the address; this is a subset of the functionality of the sag.

c

Do not include comments in addresses. This should only be used if you have to work around a

remote mailer that gets confused by comments. This strips addresses of the form “Phrase

<address>” or “address (Comment)” down to just “address”.

C‡ If mail is received from a mailer with this ag set, any addresses in the header that do not have

an at sign (“@”) after being rewritten by ruleset three will have the “@domain” clause from

the sender envelope address tacked on. This allows mail with headers of the form:

Sendmail Installation and Operation Guide

SMM:08-59

From: usera@hosta

To: userb@hostb, userc

to be rewritten as:

From: usera@hosta

To: userb@hostb, userc@hosta

automatically. Howev er, it doesn’t really work reliably.

d

Do not include angle brackets around route-address syntax addresses. This is useful on mailers

that are going to pass addresses to a shell that might interpret angle brackets as I/O redirection.

However, it does not protect against other shell metacharacters. Therefore, passing addresses

to a shell should not be considered secure.

D† This mailer wants a “Date:” header line.

e

This mailer is expensive to connect to, so try to avoid connecting normally; any necessary con-

nection will occur during a queue run. See also option HoldExpensive.

E

Escape lines beginning with “From ” in the message with a ‘>’ sign.

f

The mailer wants af fromag, but only if this is a network forward operation (i.e., the mailer

will give an error if the executing user does not have special permissions).

F† This mailer wants a “From:” header line.

g

Normally, sendmail sends internally generated email (e.g., error messages) using the null

return address as required by RFC 1123. However, some mailers don’t accept a null return

address. If necessary, you can set the gag to prevent sendmail from obeying the standards;

error messages will be sent as from the MAILER-DAEMON (actually, the value of the $n

macro).

h

Upper case should be preserved in host names (the $@ portion of the mailer triplet resolved

from ruleset 0) for this mailer.

i

Do User Database rewriting on envelope sender address.

I

This ag is deprecated and will be removed from a future version. This mailer will be speak-

ing SMTP to another sendmail — as such it can use special protocol features. This ag should

not be used except for debugging purposes because it uses VERB as SMTP command.

j

Do User Database rewriting on recipients as well as senders.

k

Normally when sendmail connects to a host via SMTP, it checks to make sure that this isn’t

accidentally the same host name as might happen if sendmail is miscongured or if a long-haul

network interface is set in loopback mode. This ag disables the loopback check. It should

only be used under very unusual circumstances.

K

Currently unimplemented. Reserved for chunking.

l

This mailer is local (i.e., nal delivery will be performed).

L

Limit the line lengths as specied in RFC 821. This deprecated option should be replaced by

the L= mail declaration. For historic reasons, the Lag also sets the 7ag.

m

This mailer can send to multiple users on the same host in one transaction. When a $u macro

occurs in the argv part of the mailer denition, that eld will be repeated as necessary for all

qualifying users. Removing this ag can defeat duplicate suppression on a remote site as each

recipient is sent in a separate transaction.

M† This mailer wants a “Message-Id:” header line.

n

Do not insert a UNIX-style “From” line on the front of the message.

o

Always run as the owner of the recipient mailbox. Normally sendmail runs as the sender for

locally generated mail or as “daemon” (actually, the user specied in the u option) when

SMM:08-60

Sendmail Installation and Operation Guide

delivering network mail. The normal behavior is required by most local mailers, which will

not allow the envelope sender address to be set unless the mailer is running as daemon. This

ag is ignored if the Sag is set.

p

Use the route-addr style reverse-path in the SMTP SMTP MAIL command rather than just the

return address; although this is required in RFC 821 section 3.1, many hosts do not process

reverse-paths properly. Rev erse-paths are ofcially discouraged by RFC 1123.

P† This mailer wants a “Return-Path:” line.

q

When an address that resolves to this mailer is veried (SMTP VRFY command), generate 250

responses instead of 252 responses. This will imply that the address is local.

r

Same as f, but sends arag.

R

Open SMTP connections from a “secure” port. Secure ports aren’t (secure, that is) except on

UNIX machines, so it is unclear that this adds anything. sendmail must be running as root to

be able to use this ag.

s

Strip quote characters (" and \) off of the address before calling the mailer.

S

Don’t reset the userid before calling the mailer. This would be used in a secure environment

where sendmail ran as root. This could be used to avoid forged addresses. If the U=eld is

also specied, this ag causes the effective user id to be set to that user.

u

Upper case should be preserved in user names for this mailer. Standards require preservation

of case in the local part of addresses, except for those address for which your system accepts

responsibility. RFC 2142 provides a long list of addresses which should be case insensitive. If

you use this ag, you may be violating RFC 2142. Note that postmaster is always treated as a

case insensitive address regardless of this ag.

U

This mailer wants UUCP-style “From” lines with the ugly “remote from <host>” on the end.

w

The user must have a valid account on this machine, i.e., getpwnam must succeed. If not, the

mail is bounced. See also the MailboxDatabase option. This is required to get “.forward”

capability.

W

Ignore long term host status information (see Section "Persistent Host Status Information").

x† This mailer wants a “Full-Name:” header line.

X

This mailer wants to use the hidden dot algorithm as specied in RFC 821; basically, any line

beginning with a dot will have an extra dot prepended (to be stripped at the other end). This

insures that lines in the message containing a dot will not terminate the message prematurely.

z

Run Local Mail Transfer Protocol (LMTP) between sendmail and the local mailer. This is a

variant on SMTP dened in RFC 2033 that is specically designed for delivery to a local mail-

box.

Z

Apply DialDelay (if set) to this mailer.

0

Don’t look up MX records for hosts sent via SMTP/LMTP. Do not apply FallbackMXhost

either.

1

Strip null characters (’\0’) when sending to this mailer.

2

Don’t use ESMTP even if offered; this is useful for broken systems that offer ESMTP but fail

on EHLO (without recovering when HELO is tried next).

3

Extend the list of characters converted to =XX notation when converting to Quoted-Printable to

include those that don’t map cleanly between ASCII and EBCDIC. Useful if you have IBM

mainframes on site.

5

If no aliases are found for this address, pass the address through ruleset 5 for possible alternate

resolution. This is intended to forward the mail to an alternate delivery spot.

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SMM:08-61

6

Strip headers to seven bits.

7

Strip all output to seven bits. This is the default if the Lag is set. Note that clearing this

option is not sufcient to get full eight bit data passed through sendmail. If the 7 option is set,

this is essentially always set, since the eighth bit was stripped on input. Note that this option

will only impact messages that didn’t hav e 87 bit MIME conversions performed.

8

If set, it is acceptable to send eight bit data to this mailer; the usual attempt to do 87 bit

MIME conversions will be bypassed.

9

If set, do limited 78 bit MIME conversions. These conversions are limited to text/plain data.

:

Check addresses to see if they begin with “:include:”; if they do, convert them to the

“*include*” mailer.

|

Check addresses to see if they begin with a ‘|’; if they do, convert them to the “prog” mailer.

/

Check addresses to see if they begin with a ‘/’; if they do, convert them to the “*le*” mailer.

@

Look up addresses in the user database.

%

Do not attempt delivery on initial receipt of a message or on queue runs unless the queued

message is selected using one of the -qI/-qR/-qS queue run modiers or an ETRN request.

!

Disable an MH hack that drops an explicit From: header if it is the same as what sendmail

would generate.

Conguration les prior to level 6 assume the ‘A’, ‘w’, ‘5’, ‘:’, ‘|’, ‘/’, and ‘@’ options on the

mailer named “local”.

The mailer with the special name “error” can be used to generate a user error. The (optional)

host eld is an exit status to be returned, and the user eld is a message to be printed. The exit sta-

tus may be numeric or one of the values USAGE, NOUSER, NOHOST, UNAVAILABLE, SOFT-

WARE, TEMPFAIL, PROT OCOL, or CONFIG to return the corresponding EX_ exit code, or an

enhanced error code as described in RFC 1893, Enhanced Mail System Status Codes. For example,

the entry:

$#error $@ NOHOST $: Host unknown in this domain

on the RHS of a rule will cause the specied error to be generated and the “Host unknown” exit sta-

tus to be returned if the LHS matches. This mailer is only functional in rulesets 0, 5, or one of the

check_* rulesets. The host eld can also contain the special token quarantine which instructs

sendmail to quarantine the current message.

The mailer with the special name “discard” causes any mail sent to it to be discarded but oth-

erwise treated as though it were successfully delivered. This mailer cannot be used in ruleset 0,

only in the various address checking rulesets.

The mailer named “local” must be dened in every conguration le. This is used to deliver

local mail, and is treated specially in several ways. Additionally, three other mailers named “prog”,

“*le*”, and “*include*” may be dened to tune the delivery of messages to programs, les, and

:include: lists respectively. They default to:

Mprog, P=/bin/sh, F=lsoDq9, T=DNS/RFC822/X-Unix, A=sh c $u

M*le*, P=[FILE], F=lsDFMPEouq9, T=DNS/RFC822/X-Unix, A=FILE $u

M*include*, P=/dev/null, F=su, A=INCLUDE $u

Builtin pathnames are [FILE] and [IPC], the former is used for delivery to les, the latter for

delivery via interprocess communication. For mailers that use [IPC] as pathname the argument vec-

tor (A=) must start with TCP or FILE for delivery via a TCP or a Unix domain socket. If TCP is

used, the second argument must be the name of the host to contact. Optionally a third argument can

be used to specify a port, the default is smtp (port 25). If FILE is used, the second argument must

be the name of the Unix domain socket.

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Sendmail Installation and Operation Guide

If the argument vector does not contain $u then sendmail will speak SMTP (or LMTP if the

mailer ag z is specied) to the mailer.

If no Eol eld is dened, then the default is "\r\n" for SMTP mailers and "\n" of others.

The Sender and Recipient rewriting sets may either be a simple ruleset id or may be two ids

separated by a slash; if so, the rst rewriting set is applied to envelope addresses and the second is

applied to headers. Setting any value to zero disables corresponding mailer-specic rewriting.

The Directory is actually a colon-separated path of directories to try. For example, the deni-

tion “D=$z:/” rst tries to execute in the recipient’s home directory; if that is not available, it tries to

execute in the root of the lesystem. This is intended to be used only on the “prog” mailer, since

some shells (such as csh) refuse to execute if they cannot read the current directory. Since the queue

directory is not normally readable by unprivileged users csh scripts as recipients can fail.

The Userid species the default user and group id to run as, overriding the DefaultUser

option (q.v.). If the S mailer ag is also specied, this user and group will be set as the effective uid

and gid for the process. This may be given as user:group to set both the user and group id; either

may be an integer or a symbolic name to be looked up in the passwd and grouples respectively. If

only a symbolic user name is specied, the group id in the passwdle for that user is used as the

group id.

The Charset eld is used when converting a message to MIME; this is the character set used

in the Content-Type: header. If this is not set, the DefaultCharSet option is used, and if that is not

set, the value “unknown-8bit” is used. WARNING: this eld applies to the sender’s mailer, not the

recipient’s mailer. For example, if the envelope sender address lists an address on the local network

and the recipient is on an external network, the character set will be set from the Charset= eld for

the local network mailer, not that of the external network mailer.

The Type= eld sets the type information used in MIME error messages as dened by RFC

1894. It is actually three values separated by slashes: the MTA-type (that is, the description of how

hosts are named), the address type (the description of e-mail addresses), and the diagnostic type (the

description of error diagnostic codes). Each of these must be a registered value or begin with “X”.

The default is “dns/rfc822/smtp”.

The m= eld species the maximum number of messages to attempt to deliver on a single

SMTP or LMTP connection. The default is innite.

The r= eld species the maximum number of recipients to attempt to deliver in a single

envelope. It defaults to 100.

The /= eld species a new root directory for the mailer. The path is macro expanded and

then passed to the “chroot” system call. The root directory is changed before the Directory eld is

consulted or the uid is changed.

The Wait= eld species the maximum time to wait for the mailer to return after sending all

data to it. This applies to mailers that have been forked by sendmail.

The Queuegroup= eld species the default queue group in which received mail should be

queued. This can be overridden by other means as explained in section ‘‘Queue Groups and Queue

Directories’’.

5.6. H — Dene Header

The format of the header lines that sendmail inserts into the message are dened by the H

line. The syntax of this line is one of the following:

Hhname: htemplate

H[?mags?]hname: htemplate

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H[?${macro}?]hname: htemplate

Continuation lines in this spec are reected directly into the outgoing message. The htemplate is

macro-expanded before insertion into the message. If the mags (surrounded by question marks)

are specied, at least one of the specied ags must be stated in the mailer denition for this header

to be automatically output. If a ${macro} (surrounded by question marks) is specied, the header

will be automatically output if the macro is set. The macro may be set using any of the normal

methods, including using the macro storage map in a ruleset. If one of these headers is in the input

it is reected to the output regardless of these ags or macros. Notice: If a ${macro} is used to set a

header, then it is useful to add that macro to class $={persistentMacros} which consists of the

macros that should be saved across queue runs.

Some headers have special semantics that will be described later.

A secondary syntax allows validation of headers as they are being read. To enable validation,

use:

HHeader: $>Ruleset

HHeader: $>+Ruleset

The indicated Ruleset is called for the specied Header, and can return $#error to reject or quaran-

tine the message or $#discard to discard the message (as with the other check_* rulesets). The

ruleset receives the header eld-body as argument, i.e., not the header eld-name; see also

${hdr_name} and ${currHeader}. The header is treated as a structured eld, that is, text in paren-

theses is deleted before processing, unless the second form $>+ is used. Note: only one ruleset can

be associated with a header; sendmail will silently ignore multiple entries.

For example, the conguration lines:

HMessage-Id: $>CheckMessageId

SCheckMessageId

R< $+ @ $+ >

$@ OK

R$*

$#error $: Illegal Message-Id header

would refuse any message that had a Message-Id: header of any of the following forms:

Message-Id: <>

Message-Id: some text

Message-Id: <legal text@domain> extra crud

A default ruleset that is called for headers which don’t hav e a specic ruleset dened for them can

be specied by:

H*: $>Ruleset

or

H*: $>+Ruleset

5.7. O — Set Option

There are a number of global options that can be set from a conguration le. Options are

represented by full words; some are also representable as single characters for back compatibility.

The syntax of this line is:

O option=value

This sets option option to be value. Note that there must be a space between the letter ‘O’ and the

name of the option. An older version is:

Oo value

where the option o is a single character. Depending on the option, value may be a string, an integer,

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Sendmail Installation and Operation Guide

a boolean (with legal values “t”, “T”, “f”, or “F”; the default is TRUE), or a time interval.

All lenames used in options should be absolute paths, i.e., starting with ’/’. Relative le-

names most likely cause surprises during operation (unless otherwise noted).

The options supported (with the old, one character names in brackets) are:

AliasFile=spec, spec, ...

[A] Specify possible alias le(s). Each spec should be in the format ‘‘class: info’’

where class: is optional and defaults to ‘‘implicit’’. Note that info is required for

all classes except “ldap”. For the “ldap” class, if info is not specied, a default

info value is used as follows:

k (&(objectClass=sendmailMTAAliasObject)

(sendmailMTAAliasName=aliases)

(|(sendmailMTACluster=${sendmailMTACluster})

(sendmailMTAHost=$j))

(sendmailMTAKey=%0))

v sendmailMTAAliasValue

Depending on how sendmail is compiled, valid classes are “implicit” (search

through a compiled-in list of alias le types, for back compatibility), “hash” (if

NEWDB is specied), “btree” (if NEWDB is specied), “dbm” (if NDBM is speci-

ed), “cdb” (if CDB is specied), “stab” (internal symbol table — not normally

used unless you have no other database lookup), “sequence” (use a sequence of

maps previously declared), “ldap” (if LDAPMAP is specied), or “nis” (if NIS is

specied). If a list of specs are provided, sendmail searches them in order.

AliasWait=timeout

[a] If set, wait up to timeout (units default to minutes) for an “@:@” entry to exist

in the alias database before starting up. If it does not appear in the timeout inter-

val issue a warning.

AllowBogusHELO

If set, allow HELO SMTP commands that don’t include a host name. Setting this

violates RFC 1123 section 5.2.5, but is necessary to interoperate with several

SMTP clients. If there is a value, it is still checked for legitimacy.

AuthMaxBits=N Limit the maximum encryption strength for the security layer in SMTP AUTH

(SASL). Default is essentially unlimited.

This allows to turn off additional

encryption in SASL if STARTTLS is already encrypting the communication,

because the existing encryption strength is taken into account when choosing an

algorithm for the security layer. For example, if STARTTLS is used and the sym-

metric cipher is 3DES, then the keylength (in bits) is 168. Hence setting Auth-

MaxBits to 168 will disable any encryption in SASL.

AuthMechanisms List of authentication mechanisms for AUTH (separated by spaces). The adver-

tised list of authentication mechanisms will be the intersection of this list and the

list of available mechanisms as determined by the Cyrus SASL library. If START-

TLS is active, EXTERNAL will be added to this list. In that case, the value of

{cert_subject} is used as authentication id.

AuthOptions

List of options for SMTP AUTH consisting of single characters with intervening

white space or commas.

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A

Use the AUTH= parameter for the MAIL

command only when authentication succeeded.

This can be used as a workaround for broken

MTAs that do not implement RFC 2554 correctly.

a

protection from active (non-dictionary) attacks

during authentication exchange.

c

require mechanisms which pass client credentials,

and allow mechanisms which can pass credentials

to do so.

d

don’t permit mechanisms susceptible to passive

dictionary attack.

f

require forward secrecy between sessions

(breaking one won’t help break next).

m

require mechanisms which provide mutual authentication

(only available if using Cyrus SASL v2 or later).

p

don’t permit mechanisms susceptible to simple

passive attack (e.g., PLAIN, LOGIN), unless a

security layer is active.

y

don’t permit mechanisms that allow anonymous login.

The rst option applies to sendmail as a client, the others to a server. Example:

O AuthOptions=p,y

would disallow ANONYMOUS as AUTH mechanism and would allow PLAIN

and LOGIN only if a security layer (e.g., provided by STARTTLS) is already

active. The options ’a’, ’c’, ’d’, ’f’, ’p’, and ’y’ refer to properties of the selected

SASL mechanisms. Explanations of these properties can be found in the Cyrus

SASL documentation.

AuthRealm

The authentication realm that is passed to the Cyrus SASL library. If no realm is

specied, $j is used. See also KNOWNBUGS.

BadRcptThrottle=N

If set and the specied number of recipients in a single SMTP transaction have

been rejected, sleep for one second after each subsequent RCPT command in that

transaction.

BlankSub=c

[B] Set the blank substitution character to c. Unquoted spaces in addresses are

replaced by this character. Defaults to space (i.e., no change is made).

CACertPath

Path to directory with certicates of CAs. This directory directory must contain

the hashes of each CA certicate as lenames (or as links to them).

CACertFile

File containing one or more CA certicates; see section about STARTTLS for

more information.

CertFingerprintAlgorithm

Specify the ngerprint algorithm (digest) to use for the presented cert. If the

option is not set, md5 is used and the macro ${cert_md5} contains the cert nger-

print. If the option is explicitly set, the specied algorithm (e.g., sha1) is used and

the macro ${cert_fp} contains the cert ngerprint.

CipherList

Specify cipher list for STARTTLS (does not apply to TLSv1.3). See ciphers(1)

for possible values.

CheckAliases

[n] Validate the RHS of aliases when rebuilding the alias database.

CheckpointInterval=N

[C] Checkpoints the queue every N (default 10) addresses sent. If your system

crashes during delivery to a large list, this prevents retransmission to any but the

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Sendmail Installation and Operation Guide

last N recipients.

ClassFactor=fact [z] The indicated factor is multiplied by the message class (determined by the

Precedence: eld in the user header and the P lines in the conguration le) and

subtracted from the priority. Thus, messages with a higher Priority: will be

favored. Defaults to 1800.

ClientCertFile

File containing the certicate of the client, i.e., this certicate is used when send-

mail acts as client (for STARTTLS).

ClientKeyFile

File containing the private key belonging to the client certicate (for STARTTLS

if sendmail runs as client).

ClientPortOptions=options

Set client SMTP options. The options are key=value pairs separated by commas.

Known keys are:

Port

Name/number of source port for connection (defaults to any free port)

Addr

Address mask (defaults INADDR_ANY)

Family

Address family (defaults to INET)

SndBufSize

Size of TCP send buffer

RcvBufSize

Size of TCP receive buffer

Modier

Options (ags) for the client

The Address mask may be a numeric address in IPv4 dot notation or IPv6 colon

notation or a network name. Note that if a network name is specied, only the

rst IP address returned for it will be used. This may cause indeterminate behav-

ior for network names that resolve to multiple addresses. Therefore, use of an

address is recommended. Modier can be the following character:

h

use name of interface for HELO command

A

don’t use AUTH when sending e-mail

S

don’t use STARTTLS when sending e-mail

If ‘‘h’’ is set, the name corresponding to the outgoing interface address (whether

chosen via the Connection parameter or the default) is used for the HELO/EHLO

command. However, the name must not start with a square bracket and it must

contain at least one dot. This is a simple test whether the name is not an IP

address (in square brackets) but a qualied hostname. Note that multiple Client-

PortOptions settings are allowed in order to give settings for each protocol family

(e.g., one for Family=inet and one for Family=inet6). A restriction placed on one

family only affects outgoing connections on that particular family.

ClientSSLOptions

A space or comma separated list of SSL related options for the client side. See

SSL_CTX_set_options(3) for a list; the available values depend on the OpenSSL

version against which

sendmail

is compiled.

By default,

SSL_OP_ALL

SSL_OP_NO_SSLv2 SSL_OP_NO_TICKET -SSL_OP_TLSEXT_PADDING are

used (if those options are available). Options can be cleared by preceding them

with a minus sign. It is also possible to specify numerical values, e.g., -0x0010.

ColonOkInAddr If set, colons are acceptable in e-mail addresses (e.g., “host:user”). If not set,

colons indicate the beginning of a RFC 822 group construct (“groupname: mem-

ber1, member2, ... memberN;”). Doubled colons are always acceptable (“node-

name::user”)

and

proper

route-addr

nesting

is

understood

(“<@relay:user@host>”). Furthermore, this option defaults on if the congura-

tion version level is less than 6 (for back compatibility). However, it must be off

for full compatibility with RFC 822.

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ConnectionCacheSize=N

[k] The maximum number of open connections that will be cached at a time. The

default is one. This delays closing the current connection until either this invoca-

tion of sendmail needs to connect to another host or it terminates. Setting it to

zero defaults to the old behavior, that is, connections are closed immediately.

Since this consumes le descriptors, the connection cache should be kept small: 4

is probably a practical maximum.

ConnectionCacheTimeout=timeout

[K] The maximum amount of time a cached connection will be permitted to idle

without activity. If this time is exceeded, the connection is immediately closed.

This value should be small (on the order of ten minutes). Before sendmail uses a

cached connection, it always sends a RSET command to check the connection; if

this fails, it reopens the connection. This keeps your end from failing if the other

end times out. The point of this option is to be a good network neighbor and

avoid using up excessive resources on the other end. The default is ve minutes.

ConnectOnlyTo=address

This can be used to override the connection address (for testing purposes).

ConnectionRateThrottle=N

If set to a positive value, allow no more than N incoming connections in a one sec-

ond period per daemon. This is intended to atten out peaks and allow the load

av erage checking to cut in. Defaults to zero (no limits).

ConnectionRateWindowSize=N

Dene the length of the interval for which the number of incoming connections is

maintained. The default is 60 seconds.

ControlSocketName=name

Name of the control socket for daemon management. A running sendmail dae-

mon can be controlled through this named socket. Available commands are: help,

mstat, restart, shutdown, and status. The status command returns the current

number of daemon children, the maximum number of daemon children, the free

disk space (in blocks) of the queue directory, and the load average of the machine

expressed as an integer. If not set, no control socket will be available. Solaris and

pre-4.4BSD kernel users should see the note in sendmail/README .

CRLFile=name

Name of le that contains certicate revocation status, useful for X.509v3 authen-

tication. Note: if a CRLFile is specied but the le is unusable, STARTTLS is

disabled.

CRLPath=name Name of directory that contains hashes pointing to certicate revocation status

les. Symbolic links can be generated with the following two (Bourne) shell

commands:

C=FileName_of_CRL

ln -s $C ‘openssl crl -noout -hash < $C‘.r0

DHParameters

This option applies to the server side only. Possible values are:

5

use precomputed 512 bit prime.

1

generate 1024 bit prime

2

generate 2048 bit prime.

i

use included precomputed 2048 bit prime (default).

none

do not use Dife-Hellman.

/path/to/le

load prime from le.

This is only required if a ciphersuite containing DSA/DH is used. The default is

‘‘i’’ which selects a precomputed, xed 2048 bit prime. If ‘‘5’’ is selected, then

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Sendmail Installation and Operation Guide

precomputed, xed primes are used. Note: this option should not be used (unless

necessary for compatibility with old implementations). If ‘‘1’’ or ‘‘2’’ is selected,

then prime values are computed during startup. Note: this operation can take a

signicant amount of time on a slow machine (several seconds), but it is only

done once at startup. If ‘‘none’’ is selected, then TLS ciphersuites containing

DSA/DH cannot be used. If a le name is specied (which must be an absolute

path), then the primes are read from it. It is recommended to generate such a le

using a command like this:

openssl dhparam -out /etc/mail/dhparams.pem 2048

If the le is not readable or contains unusable data, the default ‘‘i’’ is used instead.

DaemonPortOptions=options

[O] Set server SMTP options. Each instance of DaemonPortOptions leads to an

additional incoming socket. The options are key=value pairs. Known keys are:

Name

User-denable name for the daemon (defaults to "Daemon#")

Port

Name/number of listening port (defaults to "smtp")

Addr

Address mask (defaults INADDR_ANY)

Family

Address family (defaults to INET)

InputMailFilters List of input mail lters for the daemon

Listen

Size of listen queue (defaults to 10)

Modier

Options (ags) for the daemon

SndBufSize

Size of TCP send buffer

RcvBufSize

Size of TCP receive buffer

children

maximum number of children per daemon, see MaxDaemonChildren.

DeliveryMode

Delivery mode per daemon, see DeliveryMode.

refuseLA

RefuseLA per daemon

delayLA

DelayLA per daemon

queueLA

QueueLA per daemon

The Name key is used for error messages and logging. The Address mask may be

a numeric address in IPv4 dot notation or IPv6 colon notation, or a network name,

or a path to a local socket. Note that if a network name is specied, only the rst

IP address returned for it will be used. This may cause indeterminate behavior for

network names that resolve to multiple addresses. Therefore, use of an address is

recommended. The Family key defaults to INET (IPv4). IPv6 users who wish to

also accept IPv6 connections should add additional Family=inet6 DaemonPor-

tOptions lines. For a local socket, use Family=local or Family=unix. The Input-

MailFilters key overrides the default list of input mail lters listed in the Input-

MailFilters option. If multiple input mail lters are required, they must be sepa-

rated by semicolons (not commas). Modier can be a sequence (without any

delimiters) of the following characters:

a

always require AUTH

b

bind to interface through which mail has been received

c

perform hostname canonication (.cf)

f

require fully qualied hostname (.cf)

s

Run smtps (SMTP over SSL) instead of smtp

u

allow unqualied addresses (.cf)

A

disable AUTH (overrides ’a’ modier)

C

don’t perform hostname canonication

E

disallow ETRN (see RFC 2476)

O

optional; if opening the socket fails ignore it

S

don’t offer STARTTLS

That is, one way to specify a message submission agent (MSA) that always

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requires AUTH is:

O DaemonPortOptions=Name=MSA, Port=587, M=Ea

The modiers that are marked with "(.cf)" have only effect in the standard cong-

uration le, in which they are available via ${daemon_ags}. Notice: Do not use

the ‘‘a’’ modier on a public accessible MTA! It should only be used for a MSA

that is accessed by authorized users for initial mail submission. Users must

authenticate to use a MSA which has this option turned on. The ags ‘‘c’’ and

‘‘C’’ can change the default for hostname canonication in the sendmail.cfle.

See the relevant documentation for FEATURE(nocanonify). The modier ‘‘f ’’ dis-

allows addresses of the form user@host unless they are submitted directly. The

ag ‘‘u’’ allows unqualied sender addresses, i.e., those without @host. ‘‘b’’

forces sendmail to bind to the interface through which the e-mail has been

received for the outgoing connection. WARNING: Use ‘‘b’’ only if outgoing

mail can be routed through the incoming connection’s interface to its destination.

No attempt is made to catch problems due to a misconguration of this parameter,

use it only for virtual hosting where each virtual interface can connect to every

possible location. This will also override possible settings via ClientPortOp-

tions. Note, sendmail will listen on a new socket for each occurrence of the Dae-

monPortOptions option in a conguration le. The modier ‘‘O’’ causes send-

mail to ignore a socket if it can’t be opened. This applies to failures from the

socket(2) and bind(2) calls.

DefaultAuthInfo Filename that contains default authentication information for outgoing connec-

tions. This le must contain the user id, the authorization id, the password (plain

text), the realm and the list of mechanisms to use on separate lines and must be

readable by root (or the trusted user) only. If no realm is specied, $j is used. If

no mechanisms are specied, the list given by AuthMechanisms is used. Notice:

this option is deprecated and will be removed in future versions. Moreover, it

doesn’t work for the MSP since it can’t read the le (the le must not be

group/world-readable otherwise sendmail will complain). Use the authinfo rule-

set instead which provides more control over the usage of the data anyway.

DefaultCharSet=charset

When a message that has 8-bit characters but is not in MIME format is converted

to MIME (see the EightBitMode option) a character set must be included in the

Content-Type: header. This character set is normally set from the Charset= eld

of the mailer descriptor. If that is not set, the value of this option is used. If this

option is not set, the value “unknown-8bit” is used.

DataFileBufferSize=threshold

Set the threshold, in bytes, before a memory-based queue data le becomes disk-

based. The default is 4096 bytes.

DeadLetterDrop=le

Denes the location of the system-wide dead.letter le, formerly hardcoded to

/usr/tmp/dead.letter. If this option is not set (the default), sendmail will not

attempt to save to a system-wide dead.letter le in the event it cannot bounce the

mail to the user or postmaster. Instead, it will rename the qf le as it has in the

past when the dead.letter le could not be opened.

DefaultUser=user:group

[u] Set the default userid for mailers to user:group. If group is omitted and user is

a user name (as opposed to a numeric user id) the default group listed in the

/etc/passwd le for that user is used as the default group. Both user and group

may be numeric. Mailers without the Sag in the mailer denition will run as

SMM:08-70

Sendmail Installation and Operation Guide

this user. Defaults to 1:1. The value can also be given as a symbolic user name.19

DelayLA=LA

When the system load average exceeds LA, sendmail will sleep for one second on

most SMTP commands and before accepting connections.

DeliverByMin=time

Set minimum time for Deliver By SMTP Service Extension (RFC 2852). If 0, no

time is listed, if less than 0, the extension is not offered, if greater than 0, it is

listed as minimum time for the EHLO keyword DELIVERBY.

DeliveryMode=x [d] Deliver in mode x. Leg al modes are:

i

Deliver interactively (synchronously)

b

Deliver in background (asynchronously)

q

Just queue the message (deliver during queue run)

d

Defer delivery and all map lookups (deliver during queue run)

Defaults to ‘‘b’’ if no option is specied, ‘‘i’’ if it is specied but given no argu-

ment (i.e., ‘‘Od’’ is equivalent to ‘‘Odi’’). Thev command line ag sets this to i.

Note: for internal reasons, ‘‘i’’ does not work if a milter is enabled which can

reject or delete recipients. In that case the mode will be changed to ‘‘b’’.

DialDelay=sleeptime

Dial-on-demand network connections can see timeouts if a connection is opened

before the call is set up. If this is set to an interval and a connection times out on

the rst connection being attempted sendmail will sleep for this amount of time

and try again. This should give your system time to establish the connection to

your service provider. Units default to seconds, so “DialDelay=5” uses a ve sec-

ond delay. Defaults to zero (no retry). This delay only applies to mailers which

have the Z ag set.

DirectSubmissionModiers=modiers

Denes ${daemon_ags} for direct (command line) submissions. If not set,

${daemon_ags} is either "CC f" if the optionG is used or "c u" otherwise.

Note that only the "CC", "c", "f", and "u" ags are checked.

DontBlameSendmail=option,option,...

In order to avoid possible cracking attempts caused by world- and group-writable

les and directories, sendmail does paranoid checking when opening most of its

support les. If for some reason you absolutely must run with, for example, a

group-writable /etc directory, then you will have to turn off this checking (at the

cost of making your system more vulnerable to attack). The possible arguments

have been described earlier. The details of these ags are described above. Use

of this option is not recommended.

DontExpandCnames

The standards say that all host addresses used in a mail message must be fully

canonical. For example, if your host is named “Cruft.Foo.ORG” and also has an

alias of “FTP.Foo.ORG”, the former name must be used at all times. This is

enforced during host name canonication ($[ ... $] lookups). If this option is set,

the protocols are ignored and the “wrong” thing is done. However, the IETF is

moving toward changing this standard, so the behavior may become acceptable.

Please note that hosts downstream may still rewrite the address to be the true

canonical name however.

19The old g option has been combined into the DefaultUser option.

Sendmail Installation and Operation Guide

SMM:08-71

DontInitGroups If set, sendmail will avoid using the initgroups(3) call. If you are running NIS,

this causes a sequential scan of the groups.byname map, which can cause your

NIS server to be badly overloaded in a large domain. The cost of this is that the

only group found for users will be their primary group (the one in the password

le), which will makele access permissions somewhat more restrictive. Has no

effect on systems that don’t hav e group lists.

DontProbeInterfaces

Sendmail normally nds the names of all interfaces active on your machine when

it starts up and adds their name to the $=w class of known host aliases. If you

have a large number of virtual interfaces or if your DNS inverse lookups are slow

this can be time consuming. This option turns off that probing. However, you

will need to be certain to include all variant names in the $=w class by some other

mechanism. If set to loopback, loopback interfaces (e.g., lo0) will not be probed.

DontPruneRoutes [R] Normally, sendmail tries to eliminate any unnecessary explicit routes when

sending an error message (as discussed in RFC 1123 § 5.2.6). For example, when

sending an error message to

<@known1,@known2,@known3:user@unknown>

sendmail will strip off the “@known1,@known2” in order to make the route as

direct as possible. However, if the R option is set, this will be disabled, and the

mail will be sent to the rst address in the route, even if later addresses are known.

This may be useful if you are caught behind a rewall.

DoubleBounceAddress=error-address

If an error occurs when sending an error message, send the error report (termed a

“double bounce” because it is an error “bounce” that occurs when trying to send

another error “bounce”) to the indicated address. The address is macro expanded

at the time of delivery. If not set, defaults to “postmaster”. If set to an empty

string, double bounces are dropped.

EightBitMode=action

[8] Set handling of eight-bit data. There are two kinds of eight-bit data: that

declared as such using the BODY=8BITMIME ESMTP declaration or the

B8BITMIME command line ag, and undeclared 8-bit data, that is, input that

just happens to be eight bits. There are three basic operations that can happen:

undeclared 8-bit data can be automatically converted to 8BITMIME, undeclared

8-bit data can be passed as-is without conversion to MIME (‘‘just send 8’’), and

declared 8-bit data can be converted to 7-bits for transmission to a non-8BIT-

MIME mailer. The possible actions are:

s

Reject undeclared 8-bit data (‘‘strict’’)

m Convert undeclared 8-bit data to MIME (‘‘mime’’)

p

Pass undeclared 8-bit data (‘‘pass’’)

In all cases properly declared 8BITMIME data will be converted to 7BIT as

needed. Note: if an automatic conversion is performed, a header with the follow-

ing format will be added:

X-MIME-Autoconverted: from OLD to NEW by $j id $i

where OLD and NEW describe the original format and the converted format,

respectively.

ErrorHeader=le-or-message

[E] Prepend error messages with the indicated message. If it begins with a slash,

it is assumed to be the pathname of a le containing a message (this is the recom-

mended setting). Otherwise, it is a literal message. The error le might contain

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Sendmail Installation and Operation Guide

the name, email address, and/or phone number of a local postmaster who could

provide assistance to end users. If the option is missing or null, or if it names a

le which does not exist or which is not readable, no message is printed.

ErrorMode=x

[e] Dispose of errors using mode x. The values for x are:

p

Print error messages (default)

q

No messages, just give exit status

m

Mail back errors

w

Write back errors (mail if user not logged in)

e

Mail back errors (when applicable) and give zero exit stat always

Note that the last mode, “e”, is for Berknet error processing and should not be

used in normal circumstances. Note, too, that mode “q”, only applies to errors

recognized before sendmail forks for background delivery.

FallbackMXhost=fallbackhost

[V] If specied, the fallbackhost acts like a very low priority MX on a host. MX

records will be looked up for this host, unless the name is surrounded by square

brackets. This is intended to be used by sites with poor network connectivity.

Messages which are undeliverable due to temporary address failures (e.g., DNS

failure) also go to the FallbackMXhost.

FallBackSmartHost=hostname

If specied, the FallBackSmartHost will be used in a last-ditch effort for a host.

This is intended to be used by sites with "fake internal DNS", e.g., a company

whose DNS accurately reects the world inside that company’s domain but not

outside.

FastSplit

If set to a value greater than zero (the default is one), it suppresses the MX

lookups on addresses when they are initially sorted, i.e., for the rst delivery

attempt. This usually results in faster envelope splitting unless the MX records

are readily available in a local DNS cache. To enforce initial sorting based on

MX records set FastSplit to zero. If the mail is submitted directly from the com-

mand line, then the value also limits the number of processes to deliver the

envelopes; if more envelopes are created they are only queued up and must be

taken care of by a queue run. Since the default submission method is via SMTP

(either from a MUA or via the MSP), the value of FastSplit is seldom used to

limit the number of processes to deliver the envelopes.

ForkEachJob

[Y] If set, deliver each job that is run from the queue in a separate process.

ForwardPath=path

[J] Set the path for searching for users’ .forward les. The default is “$z/.for-

ward”. Some sites that use the automounter may prefer to change this to

“/var/forward/$u” to search a le with the same name as the user in a system

directory. It can also be set to a sequence of paths separated by colons; sendmail

stops at the rst le it can successfully and safely open. For example, “/var/for-

ward/$u:$z/.forward” will search rst in /var/forward/username and then in ˜user-

name/.forward (but only if the rst le does not exist).

HeloName=nameSet the name to be used for HELO/EHLO (instead of $j).

HelpFile=le

[H] Specify the help le for SMTP. If nole name is specied, "helple" is used.

If the help le does not exist (cannot be opened for reading) sendmail will print a

note including its version in response to a HELP command. To avoid providing

this information to a client specify an empty le.

HoldExpensive

[c] If an outgoing mailer is marked as being expensive, don’t connect immedi-

ately.

Sendmail Installation and Operation Guide

SMM:08-73

HostsFile=path

The path to the hosts database, normally “/etc/hosts”. This option is only con-

sulted when sendmail is canonifying addresses, and then only when “les” is in

the “hosts” service switch entry. In particular, this le is never used when looking

up host addresses; that is under the control of the system gethostbyname(3) rou-

tine.

HostStatusDirectory=path

The location of the long term host status information. When set, information

about the status of hosts (e.g., host down or not accepting connections) will be

shared between all sendmail processes; normally, this information is only held

within a single queue run. This option requires a connection cache of at least 1 to

function. If the option begins with a leading ‘/’, it is an absolute pathname; other-

wise, it is relative to the mail queue directory. A suggested value for sites desiring

persistent host status is “.hoststat” (i.e., a subdirectory of the queue directory).

IgnoreDots

[i] Do not treat leading dots in incoming messages in a special way, e.g., as end of

a message if it is the only character in a line. This is always disabled when read-

ing SMTP mail.

InputMailFilters=name,name,...

A comma separated list of lters which determines which lters (see the "X —

Mail Filter (Milter) Denitions" section) and the invocation sequence are con-

tacted for incoming SMTP messages. If none are set, no lters will be contacted.

LDAPDefaultSpec=spec

Sets a default map specication for LDAP maps. The value should only contain

LDAP specic settings such as “-h host -p port -d bindDN”. The settings will be

used for all LDAP maps unless the individual map specication overrides a set-

ting. This option should be set before any LDAP maps are dened.

LogLevel=n

[L] Set the log level to n. Defaults to 9.

Mx value

[no long version] Set the macro x to value. This is intended only for use from the

command line. TheMag is preferred.

MailboxDatabase Type of lookup to nd information about local mailboxes, defaults to ‘‘pw’’ which

uses getpwnam. Other types can be introduced by adding them to the source

code, see libsm/mbdb.c for details.

UseMSP

Use as mail submission program, i.e., allow group writable queue les if the

group is the same as that of a set-group-ID sendmail binary. See the le send-

mail/SECURITY in the distribution tarball.

MatchGECOS

[G] Allow fuzzy matching on the GECOS eld. If this ag is set, and the usual

user name lookups fail (that is, there is no alias with this name and a getpwnam

fails), sequentially search the password le for a matching entry in the GECOS

eld. This also requires that MATCHGECOS be turned on during compilation.

This option is not recommended.

MaxAliasRecursion=N

The maximum depth of alias recursion (default: 10).

MaxDaemonChildren=N

If set, sendmail will refuse connections when it has more than N children process-

ing incoming mail or automatic queue runs. This does not limit the number of

outgoing connections. If the default DeliveryMode (background) is used, then

sendmail may create an almost unlimited number of children (depending on the

number of transactions and the relative execution times of mail receiption and

mail delivery). If the limit should be enforced, then a DeliveryMode other than

background must be used. If not set, there is no limit to the number of children --

SMM:08-74

Sendmail Installation and Operation Guide

that is, the system load average controls this.

MaxHeadersLength=N

If set to a value greater than zero it species the maximum length of the sum of all

headers. This can be used to prevent a denial of service attack. The default is

32K.

MaxHopCount=N

[h] The maximum hop count. Messages that have been processed more than N

times are assumed to be in a loop and are rejected. Defaults to 25.

MaxMessageSize=N

Specify the maximum message size to be advertised in the ESMTP EHLO

response. Messages larger than this will be rejected. If set to a value greater than

zero, that value will be listed in the SIZE response, otherwise SIZE is advertised

in the ESMTP EHLO response without a parameter.

MaxMimeHeaderLength=N[/M]

Sets the maximum length of certain MIME header eld values to N characters.

These MIME header elds are determined by being a member of class {check-

MIMETextHeaders}, which currently contains only the header Content-Descrip-

tion. For some of these headers which take parameters, the maximum length of

each parameter is set to M if specied. If /M is not specied, one half of N will be

used. By default, these values are 2048 and 1024, respectively. To allow any

length, a value of 0 can be specied.

MaxNOOPCommands=N

Override the default of MAXNOOPCOMMANDS for the number of useless

commands, see Section "Measures against Denial of Service Attacks".

MaxQueueChildren=N

When set, this limits the number of concurrent queue runner processes to N. This

helps to control the amount of system resources used when processing the queue.

When there are multiple queue groups dened and the total number of queue run-

ners for these queue groups would exceed MaxQueueChildren then the queue

groups will not all run concurrently. That is, some portion of the queue groups

will run concurrently such that MaxQueueChildren will not be exceeded, while

the remaining queue groups will be run later (in round robin order). See also

MaxRunnersPerQueue and the section Queue Group Declaration. Notice: send-

mail does not count individual queue runners, but only sets of processes that act

on a workgroup. Hence the actual number of queue runners may be lower than

the limit imposed by MaxQueueChildren. This discrepancy can be large if some

queue runners have to wait for a slow server and if short intervals are used.

MaxQueueRunSize=N

The maximum number of jobs that will be processed in a single queue run. If not

set, there is no limit on the size. If you have very large queues or a very short

queue run interval this could be unstable. However, since the rst N jobs in queue

directory order are run (rather than the N highest priority jobs) this should be set

as high as possible to avoid “losing” jobs that happen to fall late in the queue

directory. Note: this option also restricts the number of entries printed by mailq.

That is, if MaxQueueRunSize is set to a value N larger than zero, then only N

entries are printed per queue group.

MaxRecipientsPerMessage=N

The maximum number of recipients that will be accepted per message in an

SMTP transaction. Note: setting this too low can interfere with sending mail from

MUAs that use SMTP for initial submission. If not set, there is no limit on the

Sendmail Installation and Operation Guide

SMM:08-75

number of recipients per envelope.

MaxRunnersPerQueue=N

This sets the default maximum number of queue runners for queue groups. Up to

N queue runners will work in parallel on a queue group’s messages. This is useful

where the processing of a message in the queue might delay the processing of

subsequent messages. Such a delay may be the result of non-erroneous situations

such as a low bandwidth connection. May be overridden on a per queue group

basis by setting the Runners option; see the section Queue Group Declaration.

The default is 1 when not set.

MeToo

[m] Send to me too, even if I am in an alias expansion. This option is deprecated

and will be removed from a future version.

Milter

This option has several sub(sub)options. The names of the suboptions are sepa-

rated by dots. At the rst level the following options are available:

LogLevel

Log level for input mail lter actions, defaults to LogLevel.

macros

Species list of macro to transmit to lters.

See list below.

The ‘‘macros’’ option has the following suboptions which specify the list of

macro to transmit to milters after a certain event occurred.

connect

After session connection start

helo

After EHLO/HELO command

envfrom

After MAIL command

envrcpt

After RCPT command

data

After DATA command.

eoh

After DATA command and header

eom

After DATA command and terminating ‘‘.’’

By default the lists of macros are empty. Example:

O Milter.LogLevel=12

O Milter.macros.connect=j, _, {daemon_name}

MinFreeBlocks=N

[b] Insist on at least N blocks free on the lesystem that holds the queue les

before accepting email via SMTP. If there is insufcient space sendmail gives a

452 response to the MAIL command. This invites the sender to try again later.

MaxQueueAge=age

If this is set to a value greater than zero, entries in the queue will be retried during

a queue run only if the individual retry time has been reached which is doubled

for each attempt. The maximum retry time is limited by the specied value.

MinQueueAge=age

Don’t process any queued jobs that have been in the queue less than the indicated

time interval. This is intended to allow you to get responsiveness by processing

the queue fairly frequently without thrashing your system by trying jobs too often.

The default units are minutes. Note: This option is ignored for queue runs that

select a subset of the queue, i.e., “q[!][I|R|S|Q][string]”

MustQuoteChars=s

Sets the list of characters that must be quoted if used in a full name that is in the

phrase part of a ‘‘phrase <address>’’ syntax. The default is ‘‘´.’’. The characters

‘‘@,;:\()[]’’ are always added to this list. Note: To avoid potential breakage of

DKIM signatures it is useful to set

SMM:08-76

Sendmail Installation and Operation Guide

O MustQuoteChars=.

Moreover, relaxed header signing should be used for DKIM signatures.

NiceQueueRun The priority of queue runners (nice(3)). This value must be greater or equal zero.

NoRecipientAction

The action to take when you receive a message that has no valid recipient headers

(To:, Cc:, Bcc:, or Apparently-To: — the last included for back compatibility with

old sendmails). It can be None to pass the message on unmodied, which violates

the protocol, Add-To to add a To: header with any recipients it can nd in the

envelope (which might expose Bcc: recipients), Add-Apparently-To to add an

Apparently-To: header (this is only for back-compatibility and is ofcially depre-

cated), Add-To-Undisclosed to add a header “To: undisclosed-recipients:;” to

make the header legal without disclosing anything, or Add-Bcc to add an empty

Bcc: header.

OldStyleHeaders [o] Assume that the headers may be in old format, i.e., spaces delimit names.

This actually turns on an adaptive algorithm: if any recipient address contains a

comma, parenthesis, or angle bracket, it will be assumed that commas already

exist. If this ag is not on, only commas delimit names. Headers are always out-

put with commas between the names. Defaults to off.

OperatorChars=charlist

[$o macro] The list of characters that are considered to be “operators”, that is,

characters that delimit tokens. All operator characters are tokens by themselves;

sequences of non-operator characters are also tokens. White space characters sep-

arate tokens but are not tokens themselves — for example, “AAA.BBB” has three

tokens, but “AAA BBB” has two. If not set, OperatorChars defaults to “. : @ [ ]”;

additionally, the characters “( ) < > , ;” are always operators. Note that Operator-

Chars must be set in the conguration le before any rulesets.

PidFile=lename Filename of the pid le. (default is _PATH_SENDMAILPID). Thelename is

macro-expanded before it is opened, and unlinked when sendmail exits.

PostmasterCopy=postmaster

[P] If set, copies of error messages will be sent to the named postmaster. Only the

header of the failed message is sent. Errors resulting from messages with a neg-

ative precedence will not be sent. Since most errors are user problems, this is

probably not a good idea on large sites, and arguably contains all sorts of privacy

violations, but it seems to be popular with certain operating systems vendors. The

address is macro expanded at the time of delivery. Defaults to no postmaster

copies.

PrivacyOptions= opt,opt,...

[p] Set the privacy options. ‘‘Privacy’’ is really a misnomer; many of these are

just a way of insisting on stricter adherence to the SMTP protocol. The options

can be selected from:

Sendmail Installation and Operation Guide

SMM:08-77

public

Allow open access

needmailhelo

Insist on HELO or EHLO command before MAIL

needexpnhelo

Insist on HELO or EHLO command before EXPN

noexpn

Disallow EXPN entirely, implies noverb.

needvrfyhelo

Insist on HELO or EHLO command before VRFY

novrfy

Disallow VRFY entirely

noetrn

Disallow ETRN entirely

noverb

Disallow VERB entirely

restrictmailq

Restrict mailq command

restrictqrun

Restrictq command line ag

restrictexpand

Restrictbv and v command line ags

noreceipts

Don’t return success DSNs20

nobodyreturn

Don’t return the body of a message with DSNs

goaway

Disallow essentially all SMTP status queries

authwarnings

Put X-Authentication-Warning: headers in messages

and log warnings

noactualrecipient

Don’t put X-Actual-Recipient lines in DSNs

which reveal the actual account that addresses map to.

The “goaway” pseudo-ag sets all ags except “noreceipts”, “restrictmailq”,

“restrictqrun”, “restrictexpand”, “noetrn”, and “nobodyreturn”.

If mailq is

restricted, only people in the same group as the queue directory can print the

queue. If queue runs are restricted, only root and the owner of the queue directory

can run the queue. The “restrictexpand” pseudo-ag instructs sendmail to drop

privileges when thebv option is given by users who are neither root nor the

TrustedUser so users cannot read private aliases, forwards, or :include: les. It

will add the “NonRootSafeAddr” to the “DontBlameSendmail” option to prevent

misleading unsafe address warnings. It also overrides thev (verbose) command

line option to prevent information leakage. Authentication Warnings add warn-

ings about various conditions that may indicate attempts to spoof the mail system,

such as using a non-standard queue directory.

ProcessTitlePrex=string

Prex the process title shown on ’ps’ listings with string. The string will be

macro processed.

QueueDirectory=dir

[Q] The QueueDirectory option serves two purposes. First, it species the direc-

tory or set of directories that comprise the default queue group. Second, it speci-

es the directory D which is the ancestor of all queue directories, and which send-

mail uses as its current working directory. When sendmail dumps core, it leaves

its core les in D. There are two cases. If dir ends with an asterisk (eg,

/var/spool/mqueue/qd*), then all of the directories or symbolic links to directories

beginning with ‘qd’ in /var/spool/mqueue will be used as queue directories of the

default queue group, and /var/spool/mqueue will be used as the working directory

D. Otherwise, dir must name a directory (usually /var/spool/mqueue): the default

queue group consists of the single queue directory dir, and the working directory

D is set to dir. To dene additional groups of queue directories, use the congura-

tion le ‘Q’ command. Do not change the queue directory structure while send-

mail is running.

20N.B.: the noreceiptsag turns off support for RFC 1891 (Delivery Status Notication).

SMM:08-78

Sendmail Installation and Operation Guide

QueueFactor=factor

[q] Use factor as the multiplier in the map function to decide when to just queue

up jobs rather than run them. This value is divided by the difference between the

current load average and the load average limit (QueueLA option) to determine

the maximum message priority that will be sent. Defaults to 600000.

QueueLA=LA

[x] When the system load average exceeds LA and the QueueFactor (q) option

divided by the difference in the current load average and the QueueLA option

plus one is less than the priority of the message, just queue messages (i.e., don’t

try to send them). Defaults to 8 multiplied by the number of processors online on

the system (if that can be determined).

QueueFileMode=mode

Default permissions for queue les (octal). If not set, sendmail uses 0600 unless

its real and effective uid are different in which case it uses 0644.

QueueSortOrder=algorithm

Sets the algorithm used for sorting the queue. Only the rst character of the value

is used. Legal values are “host” (to order by the name of the rst host name of the

rst recipient), “lename” (to order by the name of the queue le name), “time”

(to order by the submission/creation time), “random” (to order randomly), “modi-

cation” (to order by the modication time of the qf le (older entries rst)),

“none” (to not order), and “priority” (to order by message priority). Host ordering

makes better use of the connection cache, but may tend to process low priority

messages that go to a single host over high priority messages that go to several

hosts; it probably shouldn’t be used on slow network links. Filename and modi-

cation time ordering saves the overhead of reading all of the queued items before

starting the queue run. Creation (submission) time ordering is almost always a

bad idea, since it allows large, bulk mail to go out before smaller, personal mail,

but may have applicability on some hosts with very fast connections. Random is

useful if several queue runners are started by hand which try to drain the same

queue since odds are they will be working on different parts of the queue at the

same time. Priority ordering is the default.

QueueTimeout=timeout

[T] A synonym for “Timeout.queuereturn”. Use that form instead of the “Queue-

Timeout” form.

RandFile

Name of le containing random data or the name of the UNIX socket if EGD is

used. A (required) prex "egd:" or "le:" species the type. STARTTLS requires

this lename if the compile ag HASURANDOMDEV is not set (see send-

mail/README).

ResolverOptions=options

[I] Set resolver options. Values can be set using +ag and cleared usingag; the

ags can be “debug”, “aaonly”, “usevc”, “primary”, “igntc”, “recurse”, “def-

names”, “stayopen”, “use_inet6”, or “dnsrch”. The string “HasWildcardMX”

(without a + or) can be specied to turn off matching against MX records when

doing name canonications. The string “WorkAroundBrokenAAAA” (without a

+ or) can be specied to work around some broken nameservers which return

SERVFAIL (a temporary failure) on T_AAAA (IPv6) lookups. Notice: it might

be necessary to apply the same (or similar) options to submit.cf too.

RequiresDirfsync This

option

can

be

used

to

override

the

compile

time

ag

REQUIRES_DIR_FSYNC at runtime by setting it to false. If the compile time

ag is not set, the option is ignored. The ag turns on support for le systems that

require to call fsync() for a directory if the meta-data in it has been changed. This

should be turned on at least for older versions of ReiserFS; it is enabled by default

Sendmail Installation and Operation Guide

SMM:08-79

for Linux. According to some information this ag is not needed anymore for

kernel 2.4.16 and newer.

RrtImpliesDsn

If this option is set, a “Return-Receipt-To:” header causes the request of a DSN,

which is sent to the envelope sender as required by RFC 1891, not to the address

given in the header.

RunAsUser=user The user parameter may be a user name (looked up in /etc/passwd) or a numeric

user id; either form can have “:group” attached (where group can be numeric or

symbolic). If set to a non-zero (non-root) value, sendmail will change to this user

id shortly after startup21. This avoids a certain class of security problems. How-

ev er, this means that all “.forward” and “:include:” les must be readable by the

indicated user and all les to be written must be writable by user Also, all le and

program deliveries will be marked unsafe unless the option DontBlameSend-

mail=NonRootSafeAddr is set, in which case the delivery will be done as user.

It is also incompatible with the SafeFileEnvironment option. In other words, it

may not actually add much to security on an average system, and may in fact

detract from security (because other le permissions must be loosened). How-

ev er, it should be useful on rewalls and other places where users don’t hav e

accounts and the aliases le is well constrained.

RecipientFactor=fact

[y] The indicated factor is added to the priority (thus lowering the priority of the

job) for each recipient, i.e., this value penalizes jobs with large numbers of recipi-

ents. Defaults to 30000.

RefuseLA=LA

[X] When the system load average exceeds LA, refuse incoming SMTP connec-

tions. Defaults to 12 multiplied by the number of processors online on the system

(if that can be determined).

RejectLogInterval=timeout

Log interval when refusing connections for this long (default: 3h).

RetryFactor=fact [Z] The factor is added to the priority every time a job is processed. Thus, each

time a job is processed, its priority will be decreased by the indicated value. In

most environments this should be positive, since hosts that are down are all too

often down for a long time. Defaults to 90000.

SafeFileEnvironment=dir

If this option is set, sendmail will do a chroot(2) call into the indicated directory

before doing anyle writes. If the le name specied by the user begins with dir,

that partial path name will be stripped off before writing, so (for example) if the

SafeFileEnvironment variable is set to “/safe” then aliases of “/safe/logs/le” and

“/logs/le” actually indicate the same le. Additionally, if this option is set, send-

mail refuses to deliver to symbolic links.

SaveFromLine

[f] Save UNIX-style “From” lines at the front of headers. Normally they are

assumed redundant and discarded.

SendMimeErrors [j] If set, send error messages in MIME format (see RFC 2045 and RFC 1344 for

details). If disabled, sendmail will not return the DSN keyword in response to an

EHLO and will not do Delivery Status Notication processing as described in

RFC 1891.

ServerCertFile

File containing the certicate of the server, i.e., this certicate is used when send-

mail acts as server (used for STARTTLS).

21When running as a daemon, it changes to this user after accepting a connection but before reading any SMTP commands.

SMM:08-80

Sendmail Installation and Operation Guide

ServerKeyFile

File containing the private key belonging to the server certicate (used for

STARTTLS).

ServerSSLOptions

A space or comma separated list of SSL related options for the server side. See

SSL_CTX_set_options(3) for a list; the available values depend on the OpenSSL

version against which

sendmail

is compiled.

By default,

SSL_OP_ALL

-SSL_OP_TLSEXT_PADDING are used (if those options are available). Options

can be cleared by preceding them with a minus sign. It is also possible to specify

numerical values, e.g., -0x0010.

ServiceSwitchFile=lename

If your host operating system has a service switch abstraction (e.g., /etc/nss-

witch.conf on Solaris or /etc/svc.conf on Ultrix and DEC OSF/1) that service will

be consulted and this option is ignored. Otherwise, this is the name of a le that

provides the list of methods used to implement particular services. The syntax is

a series of lines, each of which is a sequence of words. Therst word is the ser-

vice name, and following words are service types. The services that sendmail

consults directly are “aliases” and “hosts.” Service types can be “dns”, “nis”,

“nisplus”, or “les” (with the caveat that the appropriate support must be com-

piled in before the service can be referenced). If ServiceSwitchFile is not speci-

ed, it defaults to /etc/mail/service.switch. If that le does not exist, the default

switch is:

aliases

les

hosts

dns nis les

The default le is “/etc/mail/service.switch”.

SevenBitInput

[7] Strip input to seven bits for compatibility with old systems. This shouldn’t be

necessary.

SharedMemoryKey

Ke y to use for shared memory segment; if not set (or 0), shared memory will not

be used. If set to -1 sendmail can select a key itself provided that also Shared-

MemoryKeyFile is set. Requires support for shared memory to be compiled into

sendmail. If this option is set, sendmail can share some data between different

instances. For example, the number of entries in a queue directory or the avail-

able space in a le system. This allows for more efcient program execution,

since only one process needs to update the data instead of each individual process

gathering the data each time it is required.

SharedMemoryKeyFile

If SharedMemoryKey is set to -1 then the automatically selected shared memory

key will be stored in the specied le.

SingleLineFromHeader

If set, From: lines that have embedded newlines are unwrapped onto one line.

This is to get around a botch in Lotus Notes that apparently cannot understand

legally wrapped RFC 822 headers.

SingleThreadDelivery

If set, a client machine will never try to open two SMTP connections to a single

server machine at the same time, even in different processes. That is, if another

sendmail is already talking to some host a new sendmail will not open another

connection. This property is of mixed value; although this reduces the load on the

other machine, it can cause mail to be delayed (for example, if one sendmail is

delivering a huge message, other sendmails won’t be able to send even small mes-

sages). Also, it requires another le descriptor (for the lock le) per connection,

Sendmail Installation and Operation Guide

SMM:08-81

so you may have to reduce the ConnectionCacheSize option to avoid running out

of per-process le descriptors. Requires the HostStatusDirectory option.

SmtpGreetingMessage=message

[$e macro] The message printed when the SMTP server starts up. Defaults to “$j

Sendmail $v ready at $b”.

SMTPUTF8

Enable runtime support for SMTPUTF8.

SoftBounce

If set, issue temporary errors (4xy) instead of permanent errors (5xy). This can be

useful during testing of a new conguration to avoid erroneous bouncing of mails.

SSLEngine

Name of SSL engine to use. The available values depend on the OpenSSL ver-

sion against which sendmail is compiled, see

openssl engine -v

for some information.

SSLEnginePath Path to dynamic library for SSL engine. This option is only useful if SSLEngine

is set. If both are set, the engine will be loaded dynamically at runtime using the

concatenation of the path, a slash "/", the string "lib", the value of SSLEngine, and

the string ".so". If only SSLEngine is set then the static version of the engine is

used.

StatusFile=le

[S] Log summary statistics in the namedle. If nole name is specied, "statis-

tics" is used. If not set, no summary statistics are saved. Thisle does not grow

in size. It can be printed using the mailstats(8) program.

SuperSafe

[s] This option can be set to True, False, Interactive, or PostMilter. If set to True,

sendmail will be super-safe when running things, i.e., always instantiate the queue

le, even if you are going to attempt immediate delivery. Sendmail always instan-

tiates the queue le before returning control to the client under any circumstances.

This should really always be set to True. The Interactive value has been intro-

duced in 8.12 and can be used together with DeliveryMode=i. It skips some syn-

chronization calls which are effectively doubled in the code execution path for

this mode. If set to PostMilter, sendmail defers synchronizing the queue le until

any milters have signaled acceptance of the message. PostMilter is useful only

when sendmail is running as an SMTP server; in all other situations it acts the

same as True.

TLSFallbacktoClear

If set, sendmail immediately tries an outbound connection again without START-

TLS after a TLS handshake failure. Note: this applies to all connections even if

TLS specic requirements are set (see rulesets tls_rcpt and tls_client ). Hence

such requirements will cause an error on a retry without STARTTLS. Therefore

they should only trigger a temporary failure so the connection is later on tried

again.

TLSSrvOptions List of options for SMTP STARTTLS for the server consisting of single charac-

ters with intervening white space or commas. The ag ‘‘V’’ disables client veri-

cation, and hence it is not possible to use a client certicate for relaying. The ag

‘‘C’’ removes the requirement for the TLS server to have a cert. This only works

under very specic circumstances and should only be used if the consequences are

understood, e.g., clients may not work with a server using this.

TempFileMode=mode

[F] The le mode for transcript les, les to which sendmail delivers directly,les

in the HostStatusDirectory, and StatusFile. It is interpreted in octal by default.

Defaults to 0600.

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Sendmail Installation and Operation Guide

Timeout.type= timeout

[r; subsumes old T option as well] Set timeout values. For more information, see

section 4.1.

TimeZoneSpec=tzinfo

[t] Set the local time zone info to tzinfo — for example, “PST8PDT”. Actually, if

this is not set, the TZ environment variable is cleared (so the system default is

used); if set but null, the user’s TZ variable is used, and if set and non-null the TZ

variable is set to this value.

TrustedUser=userThe user parameter may be a user name (looked up in /etc/passwd) or a numeric

user id. Trusted user for le ownership and starting the daemon. If set, generated

alias databases and the control socket (if congured) will automatically be owned

by this user.

TryNullMXList [w] If this system is the “best” (that is, lowest preference) MX for a given host, its

conguration rules should normally detect this situation and treat that condition

specially by forwarding the mail to a UUCP feed, treating it as local, or whatever.

However, in some cases (such as Internet rewalls) you may want to try to con-

nect directly to that host as though it had no MX records at all. Setting this option

causes sendmail to try this. The downside is that errors in your conguration are

likely to be diagnosed as “host unknown” or “message timed out” instead of

something more meaningful. This option is disrecommended.

UnixFromLine=fromline

[$l macro] Denes the format used when sendmail must add a UNIX-style From_

line (that is, a line beginning “From<space>user”). Defaults to “From $g $d”.

Don’t change this unless your system uses a different UNIX mailbox format (very

unlikely).

UnsafeGroupWrites

If set (default), :include: and .forward les that are group writable are considered

“unsafe”, that is, they cannot reference programs or write directly to les. World

writable :include: and .forward les are always unsafe. Note: use DontBlame-

Sendmail instead; this option is deprecated.

UseCompressedIPv6Addresses

If set, the compressed format of IPv6 addresses, such as IPV6:::1, will be used,

instead of the uncompressed format, such as IPv6:0:0:0:0:0:0:0:1.

UseErrorsTo

[l] If there is an “Errors-To:” header, send error messages to the addresses listed

there. They normally go to the envelope sender. Use of this option causes send-

mail to violate RFC 1123. This option is disrecommended and deprecated.

UserDatabaseSpec=udbspec

[U] The user database specication.

Verbose

[v] Run in verbose mode. If this is set, sendmail adjusts options HoldExpensive

(old c) and DeliveryMode (old d) so that all mail is delivered completely in a sin-

gle job so that you can see the entire delivery process. Option Verbose should

never be set in the conguration le; it is intended for command line use only.

Note that the use of option Verbose can cause authentication information to leak,

if you use a sendmail client to authenticate to a server. If the authentication mech-

anism uses plain text passwords (as with LOGIN or PLAIN), then the password

could be compromised. To avoid this, do not install sendmail set-user-ID root,

and disable the VERB SMTP command with a suitable PrivacyOptions setting.

XscriptFileBufferSize=threshold

Set the threshold, in bytes, before a memory-based queue transcript le becomes

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SMM:08-83

disk-based. The default is 4096 bytes.

All options can be specied on the command line using the O or o ag, but most will cause send-

mail to relinquish its set-user-ID permissions. The options that will not cause this are SevenBitIn-

put [7], EightBitMode [8], MinFreeBlocks [b], CheckpointInterval [C], DeliveryMode [d], Error-

Mode [e], IgnoreDots [i], SendMimeErrors [j], LogLevel [L], MeToo [m], OldStyleHeaders [o], Pri-

vacyOptions [p], SuperSafe [s], Verbose [v], QueueSortOrder, MinQueueAge, DefaultCharSet, Dial

Delay, NoRecipientAction, ColonOkInAddr, MaxQueueRunSize, SingleLineFromHeader, and

AllowBogusHELO. Actually, PrivacyOptions [p] given on the command line are added to those

already specied in the sendmail.cfle, i.e., they can’t be reset. Also, M (dene macro) when

dening the r or s macros is also considered “safe”.

5.8. P — Precedence Denitions

Values for the “Precedence:” eld may be dened using the P control line. The syntax of this

eld is:

Pname=num

When the name is found in a “Precedence:” eld, the message class is set to num. Higher numbers

mean higher precedence. Numbers less than zero have the special property that if an error occurs

during processing the body of the message will not be returned; this is expected to be used for

“bulk” mail such as through mailing lists. The default precedence is zero. For example, our list of

precedences is:

Prst-class=0

Pspecial-delivery=100

Plist=30

Pbulk=60

Pjunk=100

People writing mailing list exploders are encouraged to use “Precedence: list”. Older versions of

sendmail (which discarded all error returns for negative precedences) didn’t recognize this name,

giving it a default precedence of zero. This allows list maintainers to see error returns on both old

and new versions of sendmail.

5.9. V — Conguration Version Level

To provide compatibility with old conguration les, the V line has been added to dene

some very basic semantics of the conguration le. These are not intended to be long term sup-

ports; rather, they describe compatibility features which will probably be removed in future releases.

N.B.: these version levels have nothing to do with the version number on the les. For exam-

ple, as of this writing version 10 cong les (specically, 8.10) used version level 9 congurations.

“Old” conguration les are dened as version level one. Version level two les make the

following changes:

(1)

Host name canonication ($[ ... $]) appends a dot if the name is recognized; this gives the

cong le a way of nding out if anything matched. (Actually, this just initializes the

“host” map with the “a.”ag — you can reset it to anything you prefer by declaring the

map explicitly.)

(2)

Default host name extension is consistent throughout processing; version level one congu-

rations turned off domain extension (that is, adding the local domain name) during certain

points in processing. Version level two congurations are expected to include a trailing dot

to indicate that the name is already canonical.

(3)

Local names that are not aliases are passed through a new distinguished ruleset ve; this can

be used to append a local relay. This behavior can be prevented by resolving the local name

with an initial ‘@’. That is, something that resolves to a local mailer and a user name of

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Sendmail Installation and Operation Guide

“vikki” will be passed through ruleset ve, but a user name of “@vikki” will have the ‘@’

stripped, will not be passed through ruleset ve, but will otherwise be treated the same as

the prior example. The expectation is that this might be used to implement a policy where

mail sent to “vikki” was handled by a central hub, but mail sent to “vikki@localhost” was

delivered directly.

Version level three les allow # initiated comments on all lines. Exceptions are backslash

escaped # marks and the $# syntax.

Version level four congurations are completely equivalent to level three for historical rea-

sons.

Version levelve conguration les change the default denition of $w to be just the rst

component of the hostname.

Version level six conguration les change many of the local processing options (such as

aliasing and matching the beginning of the address for ‘|’ characters) to be mailer ags; this allows

ne-grained control over the special local processing. Level six conguration les may also use

long option names. The ColonOkInAddr option (to allow colons in the local-part of addresses)

defaults on for lower numbered conguration les; the conguration le requires some additional

intelligence to properly handle the RFC 822 group construct.

Version level sev en conguration les used new option names to replace old macros ($e

became SmtpGreetingMessage, $l became UnixFromLine, and $o became OperatorChars.

Also, prior to version seven, the F=qag (use 250 instead of 252 return value for SMTP VRFY com-

mands) was assumed.

Version level eight conguration les allow $# on the left hand side of ruleset lines.

Version level nine conguration les allow parentheses in rulesets, i.e. they are not treated as

comments and hence removed.

Version level ten conguration les allow queue group denitions.

The V line may have an optional /vendor to indicate that this conguration le uses modica-

tions specic to a particular vendor22. You may use “/Berkeley” to emphasize that this congura-

tion le uses the Berkeley dialect of sendmail.

5.10. K — Key File Declaration

Special maps can be dened using the line:

Kmapname mapclass arguments

The mapname is the handle by which this map is referenced in the rewriting rules. The mapclass is

the name of a type of map; these are compiled in to sendmail. The arguments are interpreted

depending on the class; typically, there would be a single argument naming the le containing the

map.

Maps are referenced using the syntax:

$( map key $@ arguments $: default $)

where either or both of the arguments or default portion may be omitted. The $@ arguments may

appear more than once. The indicated key and arguments are passed to the appropriate mapping

function. If it returns a value, it replaces the input. If it does not return a value and the default is

specied, the default replaces the input. Otherwise, the input is unchanged.

22And of course, vendors are encouraged to add themselves to the list of recognized vendors by editing the routine setvendor in

conf.c. Please send e-mail to sendmail@Sendmail.ORG to register your vendor dialect.

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The arguments are passed to the map for arbitrary use. Most map classes can interpolate

these arguments into their values using the syntax “%n” (where n is a digit) to indicate the corre-

sponding argument. Argument “%0” indicates the database key. For example, the rule

R$ ! $+

$: $(uucp $1 $@ $2 $: $2 @ $1 . UUCP $)

looks up the UUCP name in a (user dened) UUCP map; if not found it turns it into “.UUCP” form.

The database might contain records like:

decvax

%1@%0.DEC.COM

research

%1@%0.ATT.COM

Note that default clauses never do this mapping.

The built-in map with both name and class “host” is the host name canonicalization lookup.

Thus, the syntax:

$(host hostname$)

is equivalent to:

$[hostname$]

There are many dened classes.

cdb

Database lookups using the cdb(3) library. Sendmail must be compiled with CDB

dened.

dbm

Database lookups using the ndbm(3) library. Sendmail must be compiled with

NDBM dened.

btree

Database lookups using the btree interface to the Berkeley DB library. Sendmail

must be compiled with NEWDB dened.

hash

Database lookups using the hash interface to the Berkeley DB library. Sendmail

must be compiled with NEWDB dened.

nis

NIS lookups. Sendmail must be compiled with NIS dened.

nisplus

NIS+ lookups. Sendmail must be compiled with NISPLUS dened. The argu-

ment is the name of the table to use for lookups, and thek andvags may be

used to set the key and value columns respectively.

hesiod

Hesiod lookups. Sendmail must be compiled with HESIOD dened.

ldap

LDAP X500 directory lookups. Sendmail must be compiled with LDAPMAP

dened. The map supports most of the standard arguments and most of the com-

mand line arguments of the ldapsearch program. Note that, by default, if a single

query matches multiple values, only the rst value will be returned unless thez

(value separator) map option is set. Also, the1 map ag will treat a multiple

value return as if there were no matches.

netinfo

NeXT NetInfo lookups. Sendmail must be compiled with NETINFO dened.

text

Textle lookups. The format of the text le is dened by thek (key eld num-

ber),v (value eld number), andz (eld delimiter) options.

ph

PH query map. Contributed and supported by Mark Roth, roth@uiuc.edu.

nsd

nsd map for IRIX 6.5 and later. Contributed and supported by Bob Mende of

SGI, mende@sgi.com.

stab

Internal symbol table lookups. Used internally for aliasing.

implicit

Sequentially try a list of available map types: hash, dbm, and cdb. It is the default

for alias les if no class is specied. If is no matching map type is found, the text

version is used for the alias le, but other maps fail to open.

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Sendmail Installation and Operation Guide

user

Looks up users using getpwnam(3). Thevag can be used to specify the name

of the eld to return (although this is normally used only to check the existence of

a user).

host

Canonies host domain names. Given a host name it calls the name server to nd

the canonical name for that host.

bestmx

Returns the best MX record for a host name given as the key. The current

machine is always preferred — that is, if the current machine is one of the hosts

listed as a lowest-preference MX record, then it will be guaranteed to be returned.

This can be used to nd out if this machine is the target for an MX record, and

mail can be accepted on that basis. If thez option is given, then all MX names

are returned, separated by the given delimiter. Note: the return value is determin-

istic, i.e., even if multiple MX records have the same preference, they will be

returned in the same order.

dns

This map requires the option -R to specify the DNS resource record type to

lookup. The following types are supported: A, AAAA, AFSDB, CNAME, MX,

NS, PTR, SRV, and TXT. A map lookup will return only one record unless thez

(value separator) option is set. Hence for some types, e.g., MX records, the return

value might be a random element of the results due to randomizing in the DNS

resolver, if only one element is returned.

arpa

Returns the ‘‘reverse’’ for the given IP (IPv4 or IPv6) address, i.e., the string for

the PTR lookup, but without trailing ip6.arpa or in-addr.arpa. For example, the

following conguration lines:

Karpa arpa

SArpa

R$+

$: $(arpa $1 $)

work like this in test mode:

sendmail -bt

ADDRESS TEST MODE (ruleset 3 NOT automatically invoked)

Enter <ruleset> <address>

> Arpa IPv6:1:2:dead:beef:9876:0:0:1

Arpa

input: IPv6 : 1 : 2 : dead : beef : 9876 : 0 : 0 : 1

Arpa

returns: 1 . 0 . 0 . 0 . 0 . 0 . 0 . 0 . 0 . 0 . 0 . 0 . 6 . 7 . 8 . 9 . f . e . e . b . d . a . e . d . 2 . 0

> Arpa 1.2.3.4

Arpa

input: 1 . 2 . 3 . 4

Arpa

returns: 4 . 3 . 2 . 1

sequence

The arguments on the ‘K’ line are a list of maps; the resulting map searches the

argument maps in order until it nds a match for the indicated key. For example,

if the key denition is:

Kmap1 ...

Kmap2 ...

Kseqmap sequence map1 map2

then a lookup against “seqmap” rst does a lookup in map1. If that is found, it

returns immediately. Otherwise, the same key is used for map2.

syslog

the key is logged via syslogd (8). The lookup returns the empty string.

switch

Much like the “sequence” map except that the order of maps is determined by the

service switch. The argument is the name of the service to be looked up; the val-

ues from the service switch are appended to the map name to create new map

names. For example, consider the key denition:

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Kali switch aliases

together with the service switch entry:

aliases

nisles

This causes a query against the map “ali” to search maps named “ali.nis” and

“ali.les” in that order.

dequote

Strip double quotes (") from a name. It does not strip backslashes, and will not

strip quotes if the resulting string would contain unscannable syntax (that is, basic

errors like unbalanced angle brackets; more sophisticated errors such as unknown

hosts are not checked). The intent is for use when trying to accept mail from sys-

tems such as DECnet that routinely quote odd syntax such as

"49ers::ubell"

A typical usage is probably something like:

Kdequote dequote

...

R$

$: $(dequote $1 $)

R$ $+

$: $>3 $1 $2

Care must be taken to prevent unexpected results; for example,

"|someprogram < input > output"

will have quotes stripped, but the result is probably not what you had in mind.

Fortunately these cases are rare.

regex

The map denition on the K line contains a regular expression. Any key input is

compared to that expression using the POSIX regular expressions routines reg-

comp(), regerr(), and regexec(). Refer to the documentation for those routines for

more information about the regular expression matching. No rewriting of the key

is done if themag is used. Without it, the key is discarded or ifs if used, it is

substituted by the substring matches, delimited by $| or the string specied with

thed option. The options available for the map are

-n

not

-f

case sensitive

-b

basic regular expressions (default is extended)

-s

substring match

-d

set the delimiter string used for -s

-a

append string to key

-m match only, do not replace/discard value

-D perform no lookup in deferred delivery mode.

Thes option can include an optional parameter which can be used to select the

substrings in the result of the lookup. For example,

-s1,3,4

The delimiter string specied via thed option is the sequence of characters after

d ending at the rst space. Hence it isn’t possible to specify a space as delimiter,

so if the option is immediately followed by a space the delimiter string is empty,

which means the substrings are joined.

Notes: to match a $ in a string, \$$ must be used. If the pattern contains spaces,

they must be replaced with the blank substitution character, unless it is space

itself.

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Sendmail Installation and Operation Guide

program

The arguments on the K line are the pathname to a program and any initial param-

eters to be passed. When the map is called, the key is added to the initial parame-

ters and the program is invoked as the default user/group id. The rst line of stan-

dard output is returned as the value of the lookup. This has many potential secu-

rity problems, and has terrible performance; it should be used only when abso-

lutely necessary.

macro

Set or clear a macro value. To set a macro, pass the value as the rst argument in

the map lookup. To clear a macro, do not pass an argument in the map lookup.

The map always returns the empty string. Example of typical usage include:

Kstorage macro

...

# set macro ${MyMacro} to the ruleset match

R$+ $: $(storage {MyMacro} $@ $1 $) $1

# set macro ${MyMacro} to an empty string

R$* $: $(storage {MyMacro} $@ $) $1

# clear macro ${MyMacro}

R$ $: $(storage {MyMacro} $) $1

arith

Perform simple arithmetic operations. The operation is given as key, currently +,

-, *, /, %, |, & (bitwise OR, AND), l (for less than), =, and r (for random) are sup-

ported. The two operands are given as arguments. The lookup returns the result

of the computation, i.e., TRUE or FALSE for comparisons, integer values other-

wise. The r operator returns a pseudo-random number whose value lies between

the rst and second operand (which requires that the rst operand is smaller than

the second). All options which are possible for maps are ignored. A simple

example is:

Kcomp arith

...

Scheck_etrn

R$* $: $(comp l $@ $&{load_avg} $@ 7 $) $1

RFALSE$# error ...

socket

The socket map uses a simple request/reply protocol over TCP or UNIX domain

sockets to query an external server. Both requests and replies are text based and

encoded as netstrings, i.e., a string "hello there" becomes:

11:hello there,

Note: neither requests nor replies end with CRLF.

The request consists of the database map name and the lookup key separated by a

space character:

<mapname> ’ ’ <key>

The server responds with a status indicator and the result (if any):

<status> ’ ’ <result>

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The status indicator species the result of the lookup operation itself and is one of

the following upper case words:

OK

the key was found, result contains the looked up value

NOTFOUNDthe key was not found, the result is empty

TEMP

a temporary failure occurred

TIMEOUT a timeout occurred on the server side

PERM

a permanent failure occurred

In case of errors (status TEMP, TIMEOUT or PERM) the result eld may contain

an explanatory message. However, the explanatory message is not used any fur-

ther by sendmail.

Example replies:

31:OK resolved.address@example.com,

56:OK error:550 5.7.1 User does not accept mail from sender,

in case of successful lookups, or:

8:NOTFOUND,

in case the key was not found, or:

55:TEMP this text explains that we had a temporary failure,

in case of a temporary map lookup failure.

The socket map uses the same syntax as milters (see Section "X — Mail Filter

(Milter) Denitions") to specify the remote endpoint, e.g.,

Ksocket mySocketMap inet:12345@127.0.0.1

If multiple socket maps dene the same remote endpoint, they will share a single

connection to this endpoint.

Most of these accept as arguments the same optional ags and a lename (or a mapname for

NIS; the lename is the root of the database path, so that “.db” or some other extension appropriate

for the database type will be added to get the actual database name). Known ags are:

o

Indicates that this map is optional — that is, if it cannot be opened, no error is

produced, and sendmail will behave as if the map existed but was empty.

N, O

If neitherN orO are specied, sendmail uses an adaptive algorithm to decide

whether or not to look for null bytes on the end of keys. It starts by trying both; if

it nds any key with a null byte it never tries again without a null byte and vice

versa. IfN is specied it never tries without a null byte and ifO is specied it

never tries with a null byte. Setting one of these can speed matches but are never

necessary. If bothN andO are specied, sendmail will never try any matches

at all — that is, everything will appear to fail.

ax

Append the string x on successful matches. For example, the default host map

appends a dot on successful matches.

Tx

Append the string x on temporary failures. For example, x would be appended if a

DNS lookup returned “server failed” or an NIS lookup could not locate a server.

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See also thetag.

f

Do not fold upper to lower case before looking up the key.

m

Match only (without replacing the value). If you only care about the existence of

a key and not the value (as you might when searching the NIS map

“hosts.byname” for example), this ag prevents the map from substituting the

value. However, The a argument is still appended on a match, and the default is

still taken if the match fails.

kkeycol

The key column name (for NIS+) or number (for text lookups). For LDAP maps

this is an LDAP lter string in which %s is replaced with the literal contents of

the lookup key and %0 is replaced with the LDAP escaped contents of the lookup

key according to RFC 2254. If the agK is used, then %1 through %9 are

replaced with the LDAP escaped contents of the arguments specied in the map

lookup.

vvalcol

The value column name (for NIS+) or number (for text lookups). For LDAP

maps this is the name of one or more attributes to be returned; multiple attributes

can be separated by commas. If not specied, all attributes found in the match

will be returned. The attributes listed can also include a type and one or more

objectClass values for matching as described in the LDAP section.

zdelim

The column delimiter (for text lookups). It can be a single character or one of the

special strings “ \n” or “ \t” to indicate newline or tab respectively. If omitted

entirely, the column separator is any sequence of white space. For LDAP and

some other maps this is the separator character to combine multiple values into a

single return string. If not set, the LDAP lookup will only return the rst match

found. For DNS maps this is the separator character at which the result of a query

is cut off if is too long.

t

Normally, when a map attempts to do a lookup and the server fails (e.g., sendmail

couldn’t contact any name server; this is not the same as an entry not being found

in the map), the message being processed is queued for future processing. Thet

ag turns off this behavior, letting the temporary failure (server down) act as

though it were a permanent failure (entry not found). It is particularly useful for

DNS lookups, where someone else’s miscongured name server can cause prob-

lems on your machine. However, care must be taken to ensure that you don’t

bounce mail that would be resolved correctly if you tried again. A common strat-

egy is to forward such mail to another, possibly better connected, mail server.

D

Perform no lookup in deferred delivery mode. This ag is set by default for the

host map.

Sspacesub

The character to use to replace space characters after a successful map lookup

(esp. useful for regex and syslog maps).

sspacesub

For the dequote map only, the character to use to replace space characters after a

successful dequote.

q

Don’t dequote the key before lookup.

Llevel

For the syslog map only, it species the level to use for the syslog call.

A

When rebuilding an alias le, theAag causes duplicate entries in the text ver-

sion to be merged. For example, two entries:

list:

user1, user2

list:

user3

would be treated as though it were the single entry

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list:

user1, user2, user3

in the presence of theAag.

Some additional ags are available for the host and dns maps:

d

delay: specify the resolver’s retransmission time interval (in seconds).

r

retry: specify the number of times to retransmit a resolver query.

The dns map has another ag:

B

basedomain: specify a domain that is always appended to queries.

Socket maps have an optional ag:

d

timeout: specify the timeout (in seconds) for communication with the socket map

server.

The following additional ags are present in the ldap map only:

ctimeout

Set the LDAP network timeout.

sendmail must be compiled with

DLDAP_OPT_NETWORK_TIMEOUT to use this ag.

R

Do not auto chase referrals. sendmail must be compiled withDLDAP_REFER-

RALS to use this ag.

n

Retrieve attribute names only.

Vsep

Retrieve both attributes name and value(s), separated by sep.

rderef

Set the alias dereference option to one of never, always, search, or nd.

sscope

Set search scope to one of base, one (one level), or sub (subtree).

hhost

LDAP server hostname. Some LDAP libraries allow you to specify multiple,

space-separated hosts for redundancy. In addition, each of the hosts listed can be

followed by a colon and a port number to override the default LDAP port.

pport

LDAP service port.

H LDAPURI

Use the specied LDAP URI instead of specifying the hostname and port sepa-

rately with theh andp options shown above. For example,

-h server.example.com -p 389 -b dc=example,dc=com

is equivalent to

-H ldap://server.example.com:389 -b dc=example,dc=com

If the LDAP library supports it, the LDAP URI format however can also request

LDAP over SSL by using ldaps:// instead of ldap://. For example:

O LDAPDefaultSpec=-H ldaps://ldap.example.com -b dc=example,dc=com

Similarly, if the LDAP library supports it, It can also be used to specify a UNIX

domain socket using ldapi://:

O LDAPDefaultSpec=-H ldapi://socketle -b dc=example,dc=com

bbase

LDAP search base.

ltimelimit

Time limit for LDAP queries.

Zsizelimit

Size (number of matches) limit for LDAP or DNS queries.

ddistinguished_name

The distinguished name to use to login to the LDAP server.

Mmethod

The method to authenticate to the LDAP server.

Should be one of

LDAP_AUTH_NONE, LDAP_AUTH_SIMPLE, or LDAP_AUTH_KRBV4.

The leading LDAP_AUTH_ can be omitted and the value is case-insensitive.

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Sendmail Installation and Operation Guide

Ppasswordle

The le containing the secret key for the LDAP_AUTH_SIMPLE authentication

method or the name of the Kerberos ticket le for LDAP_AUTH_KRBV4.

1

Force LDAP searches to only succeed if a single match is found. If multiple val-

ues are found, the search is treated as if no match was found.

wversion

Set the LDAP API/protocol version to use. The default depends on the LDAP

client libraries in use. For example,w 3 will cause sendmail to use LDAPv3

when communicating with the LDAP server.

K

Treat the LDAP search key as multi-argument and replace %1 through %9 in the

key with the LDAP escaped contents of the lookup arguments specied in the map

lookup.

The dbm map appends the strings “.pag” and “.dir” to the givenlename; the hash and btree

maps append “.db”. For example, the map specication

Kuucp dbm o N /etc/mail/uucpmap

species an optional map named “uucp” of class “dbm”; it always has null bytes at the end of every

string, and the data is located in /etc/mail/uucpmap.{dir,pag}.

The program makemap(8) can be used to build database-oriented maps. It takes at least the

following ags (for a complete list see its man page):

f

Do not fold upper to lower case in the map.

N

Include null bytes in keys.

o

Append to an existing (old) le.

r

Allow replacement of existing keys; normally, re-inserting an existing key is an

error.

v

Print what is happening.

The sendmail daemon does not have to be restarted to read the new maps as long as you change

them in place; le locking is used so that the maps won’t be read while they are being updated.

New classes can be added in the routine setupmaps in le conf.c.

5.11. Q — Queue Group Declaration

In addition to the option QueueDirectory, queue groups can be declared that dene a (group

of) queue directories under a common name. The syntax is as follows:

Qname {,eld=value }+

where name is the symbolic name of the queue group under which it can be referenced in various

places and the “eld=value” pairs dene attributes of the queue group. The name must only consist

of alphanumeric characters. Fields are:

Flags

Flags for this queue group.

Nice

The nice(2) increment for the queue group. This value must be greater or equal

zero.

Interval

The time between two queue runs.

Path

The queue directory of the group (required).

Runners

The number of parallel runners processing the queue. Note that F=f must be set if

this value is greater than one.

Jobs

The maximum number of jobs (messages delivered) per queue run.

recipients

The maximum number of recipients per envelope. Envelopes with more than this

number of recipients will be split into multiple envelopes in the same queue direc-

tory. The default value 0 means no limit.

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Only the rst character of the eld name is checked.

By default, a queue group named mqueue is dened that uses the value of the QueueDirectory

option as path. Notice: all paths that are used for queue groups must be subdirectories of QueueDi-

rectory. Since they can be symbolic links, this isn’t a real restriction, If QueueDirectory uses a

wildcard, then the directory one level up is considered the ‘‘base’’ directory which all other queue

directories must share. Please make sure that the queue directories do not overlap, e.g., do not spec-

ify

O QueueDirectory=/var/spool/mqueue/*

Qone, P=/var/spool/mqueue/dir1

Qtwo, P=/var/spool/mqueue/dir2

because this also includes “dir1” and “dir2” in the default queue group. However,

O QueueDirectory=/var/spool/mqueue/main*

Qone, P=/var/spool/mqueue/dir

Qtwo, P=/var/spool/mqueue/other*

is a valid queue group specication.

Options listed in the ‘‘Flags’’eld can be used to modify the behavior of a queue group. The

‘‘f’’ag must be set if multiple queue runners are supposed to work on the entries in a queue group.

Otherwise sendmail will work on the entries strictly sequentially.

The ‘‘Interval’’eld sets the time between queue runs. If no queue group specic interval is

set, then the parameter of the -q option from the command line is used.

To control the overall number of concurrently active queue runners the option

MaxQueueChildren can be set. This limits the number of processes used for running the queues to

MaxQueueChildren, though at any one time fewer processes may be active as a result of queue

options, completed queue runs, system load, etc.

The maximum number of queue runners for an individual queue group can be controlled via

the Runners option. If set to 0, entries in the queue will not be processed, which is useful to ‘‘quar-

antine’’ queue les. The number of runners per queue group may also be set with the option

MaxRunnersPerQueue, which applies to queue groups that have no individual limit. That is, the

default value for Runners is MaxRunnersPerQueue if set, otherwise 1.

The eld Jobs describes the maximum number of jobs (messages delivered) per queue run,

which is the queue group specic value of MaxQueueRunSize.

Notice: queue groups should be declared after all queue related options have been set because

queue groups take their defaults from those options. If an option is set after a queue group declara-

tion, the values of options in the queue group are set to the defaults of sendmail unless explicitly set

in the declaration.

Each envelope is assigned to a queue group based on the algorithm described in section

‘‘Queue Groups and Queue Directories’’.

5.12. X — Mail Filter (Milter) Denitions

The sendmail Mail Filter API (Milter) is designed to allow third-party programs access to

mail messages as they are being processed in order to lter meta-information and content. They are

declared in the conguration le as:

Xname {,eld=value }*

where name is the name of the lter (used internally only) and the “eld=name” pairs dene

attributes of the lter. Also see the documentation for the InputMailFilters option for more infor-

mation.

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Fields are:

Socket

The socket specication

Flags

Specialags for this lter

Timeouts

Timeouts for this lter

Only the rst character of the eld name is checked (it’s case-sensitive).

The socket specication is one of the following forms:

S=inet: port @ host

S=inet6: port @ host

S=local: path

The rst two describe an IPv4 or IPv6 socket listening on a certain port at a given host or IP

address. Thenal form describes a named socket on the lesystem at the given path.

The following ags may be set in the lter description.

R

Reject connection if lter unavailable.

T

Temporary fail connection if lter unavailable.

If neither F=R nor F=T is specied, the message is passed through sendmail in case of lter

errors as if the failing lters were not present.

The timeouts can be set using the four elds inside of the T= equate:

C

Timeout for connecting to a lter. If set to 0, the system’s connect() timeout will be used.

S

Timeout for sending information from the MTA to alter.

R

Timeout for reading reply from the lter.

E

Overall timeout between sending end-of-message to lter and waiting for the nal acknowl-

edgment.

Note the separator between each timeout eld is a ’;’. The default values (if not set) are:

T=C:5m;S:10s;R:10s;E:5m where s is seconds and m is minutes.

Examples:

Xlter1, S=local:/var/run/f1.sock, F=R

Xlter2, S=inet6:999@localhost, F=T, T=S:1s;R:1s;E:5m

Xlter3, S=inet:3333@localhost, T=C:2m

5.13. The User Database

The user database is deprecated in favor of ‘‘virtusertable’’ and ‘‘genericstable’’ as explained

in the le cf/README. If you have a version of sendmail with the user database package com-

piled in, the handling of sender and recipient addresses is modied.

The location of this database is controlled with the UserDatabaseSpec option.

5.13.1. Structure of the user database

The database is a sorted (BTree-based) structure. User records are stored with the key:

user-name:eld-name

The sorted database format ensures that user records are clustered together. Meta-information is

always stored with a leading colon.

Field names dene both the syntax and semantics of the value. Denedelds include:

maildrop

The delivery address for this user. There may be multiple values of this

record. In particular, mailing lists will have one maildrop record for each user

Sendmail Installation and Operation Guide

SMM:08-95

on the list.

mailname

The outgoing mailname for this user. For each outgoing name, there should

be an appropriate maildrop record for that name to allow return mail. See also

:default:mailname.

mailsender

Changes any mail sent to this address to have the indicated envelope sender.

This is intended for mailing lists, and will normally be the name of an appro-

priate -request address. It is very similar to the owner-list syntax in the alias

le.

fullname

The full name of the user.

ofce-address

The ofce address for this user.

ofce-phone

The ofce phone number for this user.

ofce-fax

The ofce FAX number for this user.

home-address

The home address for this user.

home-phone

The home phone number for this user.

home-fax

The home FAX number for this user.

project

A (short) description of the project this person is afliated with. In the Uni-

versity this is often just the name of their graduate advisor.

plan

A pointer to a le from which plan information can be gathered.

As of this writing, only a few of these elds are actually being used by sendmail: mail-

drop and mailname. Anger program that uses the other elds is planned.

5.13.2. User database semantics

When the rewriting rules submit an address to the local mailer, the user name is passed

through the alias le. If no alias is found (or if the alias points back to the same address), the

name (with “:maildrop” appended) is then used as a key in the user database. If no match

occurs (or if the maildrop points at the same address), forwarding is tried.

If the rst token of the user name returned by ruleset 0 is an “@” sign, the user database

lookup is skipped. The intent is that the user database will act as a set of defaults for a cluster

(in our case, the Computer Science Division); mail sent to a specic machine should ignore

these defaults.

When mail is sent, the name of the sending user is looked up in the database. If that user

has a “mailname” record, the value of that record is used as their outgoing name. For example, I

might have a record:

eric:mailname

Eric.Allman@CS.Berkeley.EDU

This would cause my outgoing mail to be sent as Eric.Allman.

If a “maildrop” is found for the user, but no corresponding “mailname” record exists, the

record “:default:mailname” is consulted. If present, this is the name of a host to override the

local host. For example, in our case we would set it to “CS.Berkeley.EDU”. The effect is that

anyone known in the database gets their outgoing mail stamped as “user@CS.Berkeley.EDU”,

but people not listed in the database use the local hostname.

5.13.3. Creating the database23

23These instructions are known to be incomplete. Other features are available which provide similar functionality, e.g., virtual

hosting and mapping local addresses into a generic form as explained in cf/README.

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Sendmail Installation and Operation Guide

The user database is built from a text le using the makemap utility (in the distribution in

the makemap subdirectory). The text le is a series of lines corresponding to userdb records;

each line has a key and a value separated by white space. The key is always in the format

described above — for example:

eric:maildrop

This le is normally installed in a system directory; for example, it might be called

/etc/mail/userdb. To make the database version of the map, run the program:

makemap btree /etc/mail/userdb < /etc/mail/userdb

Then create a cong le that uses this. For example, using the V8 M4 conguration, include the

following line in your .mc le:

dene(`confUSERDB_SPEC´, /etc/mail/userdb)

6. OTHER CONFIGURATION

There are some conguration changes that can be made by recompiling sendmail. This section

describes what changes can be made and what has to be modied to make them. In most cases this

should be unnecessary unless you are porting sendmail to a new environment.

6.1. Parameters in devtools/OS/$oscf

These parameters are intended to describe the compilation environment, not site policy, and

should normally be dened in the operating system conguration le. This section needs a com-

plete rewrite.

NDBM

If set, the new version of the DBM library that allows multiple databases will be

used. If neither CDB, NDBM, nor NEWDB are set, a much less efcient method

of alias lookup is used.

CDB

If set, use the cdb (tinycdb) package.

NEWDB

If set, use the new database package from Berkeley (from 4.4BSD). This package

is substantially faster than DBM or NDBM. If NEWDB and NDBM are both set,

sendmail will read DBM les, but will create and use NEWDB les.

NIS

Include support for NIS. If set together with both NEWDB and NDBM, sendmail

will create both DBM and NEWDB les if and only if an alias le includes the

substring “/yp/” in the name.

This is intended for compatibility with Sun

Microsystems’ mkalias program used on YP masters.

NISPLUS

Compile in support for NIS+.

NETINFO

Compile in support for NetInfo (NeXT stations).

LDAPMAP

Compile in support for LDAP X500 queries. Requires libldap and liblber from

the Umich LDAP 3.2 or 3.3 release or equivalent libraries for other LDAP

libraries such as OpenLDAP.

HESIOD

Compile in support for Hesiod.

MAP_NSD

Compile in support for IRIX NSD lookups.

MAP_REGEX

Compile in support for regular expression matching.

DNSMAP

Compile in support for DNS map lookups in the sendmail.cfle.

PH_MAP

Compile in support for ph lookups.

SASL

Compile in support for SASL, a required component for SMTP Authentication

support.

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STARTTLS

Compile in support for STARTTLS.

EGD

Compile in support for the "Entropy Gathering Daemon" to provide better random

data for TLS.

TCPWRAPPERS Compile in support for TCP Wrappers.

_PATH_SENDMAILCF

The pathname of the sendmail.cf le.

_PATH_SENDMAILPID

The pathname of the sendmail.pid le.

SM_CONF_SHM

Compile in support for shared memory, see section about "/var/spool/mqueue".

MILTER

Compile in support for contacting external mail lters built with the Milter API.

There are also several compilation ags to indicate the environment such as “_AIX3” and

“_SCO_unix_”. See the sendmail/README le for the latest scoop on these ags.

6.1.1. For Future Releases

sendmail often contains compile time options For Future Releases (prex _FFR_) which

might be enabled in a subsequent version or might simply be removed as they turned out not to

be really useful. These features are usually not documented but if they are, then the required

(FFR) compile time options are listed here for rulesets and macros, and in cf/README for

mc/cf options. FFR compile times options must be enabled when the sendmail binary is built

from source. Enabled FFRs in a binary can be listed with

sendmail -d0.13 < /dev/null | grep FFR

6.2. Parameters in sendmail/conf.h

Parameters and compilation options are dened in conf.h. Most of these need not normally

be tweaked; common parameters are all in sendmail.cf. However, the sizes of certain primitive vec-

tors, etc., are included in this le. The numbers following the parameters are their default value.

This document is not the best source of information for compilation ags in conf.h — see

sendmail/README or sendmail/conf.h itself.

MAXLINE [2048]

The maximum line length of any input line. If message lines exceed this

length they will still be processed correctly; however, header lines, congura-

tion le lines, alias lines, etc., must t within this limit.

MAXNAME [256]

The maximum length of any name, such as a host or a user name.

MAXPV [256]

The maximum number of parameters to any mailer. This limits the number of

recipients that may be passed in one transaction. It can be set to any arbitrary

number above about 10, since sendmail will break up a delivery into smaller

batches as needed. A higher number may reduce load on your system, how-

ev er.

MAXQUEUEGROUPS [50]

The maximum number of queue groups.

MAXATOM [1000] The maximum number of atoms (tokens) in a single address. For example, the

address “eric@CS.Berkeley.EDU” is seven atoms.

MAXMAILERS [25]The maximum number of mailers that may be dened in the conguration le.

This value is dened in include/sendmail/sendmail.h.

MAXRWSETS [200]The maximum number of rewriting sets that may be dened. The rst half of

these are reserved for numeric specication (e.g., ‘‘S92’’), while the upper half

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Sendmail Installation and Operation Guide

are reserved for auto-numbering (e.g., ‘‘Sfoo’’). Thus, with a value of 200 an

attempt to use ‘‘S99’’ will succeed, but ‘‘S100’’ will fail.

MAXPRIORITIES [25]

The maximum number of values for the “Precedence:” eld that may be

dened (using the P line in sendmail.cf).

MAXUSERENVIRON [100]

The maximum number of items in the user environment that will be passed to

subordinate mailers.

MAXMXHOSTS [100]

The maximum number of MX records we will accept for any single host.

MAXMAPSTACK [12]

The maximum number of maps that may be "stacked" in a sequence class

map.

MAXMIMEARGS [20]

The maximum number of arguments in a MIME Content-Type: header; addi-

tional arguments will be ignored.

MAXMIMENESTING [20]

The maximum depth to which MIME messages may be nested (that is, nested

Message or Multipart documents; this does not limit the number of compo-

nents in a single Multipart document).

MAXDAEMONS [10]

The maximum number of sockets sendmail will open for accepting connec-

tions on different ports.

MAXMACNAMELEN [25]

The maximum length of a macro name.

A number of other compilation options exist. These specify whether or not specic code should be

compiled in. Ones marked with † are 0/1 valued.

NETINET†

If set, support for Internet protocol networking is compiled in. Previous ver-

sions of sendmail referred to this as DAEMON; this old usage is now incorrect.

Defaults on; turn it off in the Makele if your system doesn’t support the

Internet protocols.

NETINET6†

If set, support for IPv6 networking is compiled in. It must be separately

enabled by adding DaemonPortOptions settings.

NETISO†

If set, support for ISO protocol networking is compiled in (it may be appropri-

ate to #dene this in the Makele instead of conf.h).

NETUNIX†

If set, support for UNIX domain sockets is compiled in. This is used for con-

trol socket support.

LOG

If set, the syslog routine in use at some sites is used. This makes an informa-

tional log record for each message processed, and makes a higher priority log

record for internal system errors. STRONGLY RECOMMENDED — if you

want no logging, turn it off in the conguration le.

MATCHGECOS†

Compile in the code to do ‘‘fuzzy matching’’ on the GECOS eld in

/etc/passwd. This also requires that the MatchGECOS option be turned on.

NAMED_BIND†

Compile in code to use the Berkeley Internet Name Domain (BIND) server to

resolve TCP/IP host names.

NOTUNIX

If you are using a non-UNIX mail format, you can set this ag to turn off spe-

cial processing of UNIX-style “From ” lines.

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USERDB†

Include the experimental Berkeley user information database package. This

adds a new lev el of local name expansion between aliasing and forwarding. It

also uses the NEWDB package. This may change in future releases.

The following options are normally turned on in per-operating-system clauses in conf.h.

IDENTPROT O†

Compile in the IDENT protocol as dened in RFC 1413. This defaults on for

all systems except Ultrix, which apparently has the interesting “feature” that

when it receives a “host unreachable” message it closes all open connections

to that host. Since some rewall gateways send this error code when you

access an unauthorized port (such as 113, used by IDENT), Ultrix cannot

receive email from such hosts.

SYSTEM5

Set all of the compilation parameters appropriate for System V.

HASFLOCK†

Use Berkeley-styleock instead of System V lockf to do le locking. Due to

the highly unusual semantics of locks across forks in lockf, this should always

be used if at all possible.

HASINITGROUPS Set this if your system has the initgroups() call (if you have multiple group

support). This is the default if SYSTEM5 is not dened or if you are on

HPUX.

HASUNAME

Set this if you have the uname(2) system call (or corresponding library rou-

tine). Set by default if SYSTEM5 is set.

HASGETDTABLESIZE

Set this if you have the getdtablesize(2) system call.

HASWAITPID

Set this if you have the haswaitpid(2) system call.

FAST_PID_RECYCLE

Set this if your system can possibly reuse the same pid in the same second of

time.

SFS_TYPE

The mechanism that can be used to get le system capacity information. The

values can be one of SFS_USTAT (use the ustat(2) syscall), SFS_4ARGS (use

the four argument statfs(2) syscall), SFS_VFS (use the two argument statfs(2)

syscall including <sys/vfs.h>), SFS_MOUNT (use the two argument statfs(2)

syscall including <sys/mount.h>), SFS_STATFS (use the two argument

statfs(2) syscall including <sys/statfs.h>), SFS_STATVFS (use the two argu-

ment statfs(2) syscall including <sys/statvfs.h>), or SFS_NONE (no way to

get this information).

LA_TYPE

The load average type. Details are described below.

The are several built-in ways of computing the load average. Sendmail tries to auto-congure them

based on imperfect guesses; you can select one using the cc optionDLA_TYPE=type, where type

is:

LA_INT

The kernel stores the load average in the kernel as an array of long integers.

The actual values are scaled by a factor FSCALE (default 256).

LA_SHORT

The kernel stores the load average in the kernel as an array of short integers.

The actual values are scaled by a factor FSCALE (default 256).

LA_FLOAT

The kernel stores the load average in the kernel as an array of double precision

oats.

LA_MACH

Use MACH-style load averages.

LA_SUBR

Call the getloadavg routine to get the load average as an array of doubles.

LA_ZERO

Always return zero as the load average. This is the fallback case.

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If type LA_INT, LA_SHORT, or LA_FLOAT is specied, you may also need to specify _PATH_UNIX

(the path to your system binary) and LA_AVENRUN (the name of the variable containing the load

av erage in the kernel; usually “_avenrun” or “avenrun”).

6.3. Conguration in sendmail/conf.c

The following changes can be made in conf.c.

6.3.1. Built-in Header Semantics

Not all header semantics are dened in the conguration le. Header lines that should

only be included by certain mailers (as well as other more obscure semantics) must be specied

in the HdrInfo table in conf.c. This table contains the header name (which should be in all lower

case) and a set of header control ags (described below), The ags are:

H_ACHECK

Normally when the check is made to see if a header line is compatible with

a mailer, sendmail will not delete an existing line. If this ag is set, send-

mail will delete even existing header lines. That is, if this bit is set and the

mailer does not have ag bits set that intersect with the required mailer

ags in the header denition in sendmail.cf, the header line is always

deleted.

H_EOH

If this header eld is set, treat it like a blank line, i.e., it will signal the end

of the header and the beginning of the message text.

H_FORCE

Add this header entry even if one existed in the message before. If a

header entry does not have this bit set, sendmail will not add another

header line if a header line of this name already existed. This would nor-

mally be used to stamp the message by everyone who handled it.

H_TRACE

If set, this is a timestamp (trace) eld. If the number of trace elds in a

message exceeds a preset amount the message is returned on the assump-

tion that it has an aliasing loop.

H_RCPT

If set, this eld contains recipient addresses. This is used by thetag to

determine who to send to when it is collecting recipients from the mes-

sage.

H_FROM

Thisag indicates that this eld species a sender. The order of these

elds in the HdrInfo table species sendmail’s preference for which eld

to return error messages to.

H_ERRORSTO

Addresses in this header should receive error messages.

H_CTE

This header is a Content-Transfer-Encoding header.

H_CTYPE

This header is a Content-Type header.

H_BCC

Strip the value from the header (for Bcc:).

Let’s look at a sample HdrInfo specication:

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struct hdrinfo

HdrInfo[] =

{

/* originator elds, most to least signicant */

"resent-sender",

H_FROM,

"resent-from",

H_FROM,

"sender",

H_FROM,

"from",

H_FROM,

"full-name",

H_ACHECK,

"errors-to",

H_FROM | H_ERRORSTO,

/* destination elds */

"to",

H_RCPT,

"resent-to",

H_RCPT,

"cc",

H_RCPT,

"bcc",

H_RCPT|H_BCC,

/* message identication and control */

"message",

H_EOH,

"text",

H_EOH,

/* trace elds */

"received",

H_TRACE | H_FORCE,

/* miscellaneous elds */

"content-transfer-encoding", H_CTE,

"content-type",

H_CTYPE,

NULL,

0,

};

This structure indicates that the “To:”, “Resent-To:”, and “Cc:” elds all specify recipient

addresses. Any “Full-Name:” eld will be deleted unless the required mailer ag (indicated in

the conguration le) is specied. The “Message:” and “Text:” elds will terminate the header;

these are used by random dissenters around the network world. The “Received:” eld will

always be added, and can be used to trace messages.

There are a number of important points here. First, header elds are not added automati-

cally just because they are in the HdrInfo structure; they must be specied in the conguration

le in order to be added to the message. Any header elds mentioned in the conguration le

but not mentioned in the HdrInfo structure have default processing performed; that is, they are

added unless they were in the message already. Second, the HdrInfo structure only species

cliched processing; certain headers are processed specially by ad hoc code regardless of the sta-

tus specied in HdrInfo. For example, the “Sender:” and “From:” elds are always scanned on

ARPANET mail to determine the sender24; this is used to perform the “return to sender” func-

tion. The “From:” and “Full-Name:” elds are used to determine the full name of the sender if

possible; this is stored in the macro $x and used in a number of ways.

6.3.2. Restricting Use of Email

If it is necessary to restrict mail through a relay, the checkcompat routine can be modied.

This routine is called for every recipient address. It returns an exit status indicating the status of

the message. The status EX_OK accepts the address, EX_TEMPFAIL queues the message for a

later try, and other values (commonly EX_UNAVAILABLE) reject the message. It is up to check-

compat to print an error message (using usrerr) if the message is rejected. For example,

24Actually, this is no longer true in SMTP; this information is contained in the envelope. The older ARPANET protocols did

not completely distinguish envelope from header.

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checkcompat could read:

int

checkcompat(to, e)

register ADDRESS *to;

register ENVELOPE *e;

{

register STAB *s;

s = stab("private", ST_MAILER, ST_FIND);

if (s != NULL && e>e_from.q_mailer != LocalMailer &&

to->q_mailer == s->s_mailer)

{

usrerr("No private net mail allowed through this machine");

return (EX_UNAVAILABLE);

}

if (MsgSize > 50000 && bitnset(M_LOCALMAILER, to>q_mailer))

{

usrerr("Message too large for non-local delivery");

e>e_ags |= EF_NORETURN;

return (EX_UNAVAILABLE);

}

return (EX_OK);

}

This would reject messages greater than 50000 bytes unless they were local. The EF_NORE-

TURNag can be set in ee_ags to suppress the return of the actual body of the message in

the error return. The actual use of this routine is highly dependent on the implementation, and

use should be limited.

6.3.3. New Database Map Classes

New key maps can be added by creating a class initialization function and a lookup func-

tion. These are then added to the routine setupmaps.

The initialization function is called as

xxx_map_init(MAP *map, char *args)

The map is an internal data structure. The args is a pointer to the portion of the conguration

le line following the map class name; ags and lenames can be extracted from this line. The

initialization function must return true if it successfully opened the map, false otherwise.

The lookup function is called as

xxx_map_lookup(MAP *map, char buf[], char **av, int *statp)

The map denes the map internally. The buf has the input key. This may be (and often is) used

destructively. The av is a list of arguments passed in from the rewrite line. The lookup function

should return a pointer to the new value. If the map lookup fails, *statp should be set to an exit

status code; in particular, it should be set to EX_TEMPFAIL if recovery is to be attempted by the

higher level code.

6.3.4. Queueing Function

The routine shouldqueue is called to decide if a message should be queued or processed

immediately. Typically this compares the message priority to the current load average. The

default denition is:

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bool

shouldqueue(pri, ctime)

long pri;

time_t ctime;

{

if (CurrentLA < QueueLA)

return false;

return (pri > (QueueFactor / (CurrentLA QueueLA + 1)));

}

If the current load average (global variable CurrentLA, which is set before this function is

called) is less than the low threshold load average (option x, variable QueueLA), shouldqueue

returns false immediately (that is, it should not queue). If the current load average exceeds the

high threshold load average (option X, variable RefuseLA), shouldqueue returns true immedi-

ately. Otherwise, it computes the function based on the message priority, the queue factor

(option q, global variable QueueFactor), and the current and threshold load averages.

An implementation wishing to take the actual age of the message into account can also

use the ctime parameter, which is the time that the message was rst submitted to sendmail.

Note that the pri parameter is already weighted by the number of times the message has been

tried (although this tends to lower the priority of the message with time); the expectation is that

the ctime would be used as an “escape clause” to ensure that messages are eventually processed.

6.3.5. Refusing Incoming SMTP Connections

The function refuseconnections returns true if incoming SMTP connections should be

refused. The current implementation is based exclusively on the current load average and the

refuse load average option (option X, global variable RefuseLA):

bool

refuseconnections()

{

return (RefuseLA > 0 && CurrentLA >= RefuseLA);

}

A more clever implementation could look at more system resources.

6.3.6. Load Average Computation

The routine getla returns the current load average (as a rounded integer). The distribution

includes several possible implementations. If you are porting to a new environment you may

need to add some new tweaks.25

6.4. Conguration in sendmail/daemon.c

The le sendmail/daemon.c contains a number of routines that are dependent on the local net-

working environment. The version supplied assumes you have BSD style sockets.

In previous releases, we recommended that you modify the routine maphostname if you

wanted to generalize $[ ... $] lookups. We now recommend that you create a new keyed map

instead.

25If you do, please send updates to sendmail@Sendmail.ORG.

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6.5. LDAP

In this section we assume that sendmail has been compiled with support for LDAP.

6.5.1. LDAP Recursion

LDAP Recursion allows you to add types to the search attributes on an LDAP map speci-

cation. The syntax is:

v ATTRIBUTE[:TYPE[:OBJECTCLASS[|OBJECTCLASS|...]]]

The new TYPEs are:

NORMAL

This attribute type species the attribute to add to the results string. This is

the default.

DN

Any matches for this attribute are expected to have a value of a fully qualied

distinguished name. sendmail will lookup that DN and apply the attributes

requested to the returned DN record.

FILTER

Any matches for this attribute are expected to have a value of an LDAP search

lter. sendmail will perform a lookup with the same parameters as the origi-

nal search but replaces the search lter with the one specied here.

URL

Any matches for this attribute are expected to have a value of an LDAP URL.

sendmail will perform a lookup of that URL and use the results from the

attributes named in that URL. Note however that the search is done using the

current LDAP connection, regardless of what is specied as the scheme,

LDAP host, and LDAP port in the LDAP URL.

Any untyped attributes are considered NORMAL attributes as described above.

The optional OBJECTCLASS (| separated) list contains the objectClass values for which

that attribute applies. If the list is given, the attribute named will only be used if the LDAP

record being returned is a member of that object class. Note that if these new value attribute

TYPEs are used in an AliasFile option setting, it will need to be double quoted to prevent send-

mail from misparsing the colons.

Note that LDAP recursion attributes which do not ultimately point to an LDAP record are

not considered an error.

6.5.1.1. Example

Since examples usually help clarify, here is an example which uses all four of the new

types:

O LDAPDefaultSpec=-h ldap.example.com -b dc=example,dc=com

Ke xample ldap

-z,

-k (&(objectClass=sendmailMTAAliasObject)(sendmailMTAKey=%0))

-v sendmailMTAAliasValue,mail:NORMAL:inetOrgPerson,

uniqueMember:DN:groupOfUniqueNames,

sendmailMTAAliasSearch:FILTER:sendmailMTAAliasObject,

sendmailMTAAliasURL:URL:sendmailMTAAliasObject

That denition species that:

• Any value in a sendmailMTAAliasValue attribute will be added to the result string regard-

less of object class.

• The mail attribute will be added to the result string if the LDAP record is a member of the

inetOrgPerson object class.

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• The uniqueMember attribute is a recursive attribute, used only in groupOfUniqueNames

records, and should contain an LDAP DN pointing to another LDAP record. The desire

here is to return the mail attribute from those DNs.

• The sendmailMTAAliasSearch attribute and sendmailMTAAliasURL are both used only if

referenced in a sendmailMTAAliasObject. They are both recursive, the rst for a new

LDAP search string and the latter for an LDAP URL.

6.6. STARTTLS

In this section we assume that sendmail has been compiled with support for STARTTLS. To

properly understand the use of STARTTLS in sendmail, it is necessary to understand at least some

basics about X.509 certicates and public key cryptography. This information can be found in

books about SSL/TLS or on WWW sites, e.g., “https://www.OpenSSL.org/”.

6.6.1. Certicates for STARTTLS

When acting as a server, sendmail requires X.509 certicates to support STARTTLS: one

as certicate for the server (ServerCertFile and corresponding private ServerKeyFile) at least

one root CA (CACertFile), i.e., a certicate that is used to sign other certicates, and a path to a

directory which contains (zero or more) other CAs (CACertPath). Thele specied via CAC-

ertFile can contain several certicates of CAs. The DNs of these certicates are sent to the

client during the TLS handshake (as part of the CerticateRequest) as the list of acceptable CAs.

However, do not list too many root CAs in that le, otherwise the TLS handshake may fail; e.g.,

error:14094417:SSL routines:SSL3_READ_BYTES:

sslv3 alert illegal parameter:s3_pkt.c:964:SSL alert number 47

You should probably put only the CA cert into that le that signed your own cert(s), or at least

only those you trust. The CACertPath directory must contain the hashes of each CA certicate

as lenames (or as links to them). Symbolic links can be generated with the following two

(Bourne) shell commands:

C=FileName_of_CA_Certicate

ln -s $C ‘openssl x509 -noout -hash < $C‘.0

A better way to do this is to use the c_rehash command that is part of the OpenSSL distribution

because it handles subject hash collisions by incrementing the number in the sufx of the le-

name of the symbolic link, e.g., .0 to .1, and so on. An X.509 certicate is also required for

authentication in client mode (ClientCertFile and corresponding private ClientKeyFile), how-

ev er, sendmail will always use STARTTLS when offered by a server. The client and server cer-

ticates can be identical. Certicates can be obtained from a certicate authority or created with

the help of OpenSSL. The required format for certicates and private keys is PEM. To allow

for automatic startup of sendmail, private keys (ServerKeyFile, ClientKeyFile) must be stored

unencrypted. The keys are only protected by the permissions of the le system. Never make a

private key available to a third party.

The options ClientCertFile, ClientKeyFile, ServerCertFile, and ServerKeyFile can take a

second le name, which must be separated from the rst with a comma (note: do not use any

spaces) to set up a second cert/key pair. This can be used to have certs of different types, e.g.,

RSA and DSA.

6.6.2. PRNG for STARTTLS

STARTTLS requires a strong pseudo random number generator (PRNG) to operate prop-

erly. Depending on the TLS library you use, it may be required to explicitly initialize the PRNG

with random data. OpenSSL makes use of /dev/urandom(4) if available (this corresponds to

the compile ag HASURANDOMDEV). On systems which lack this support, a random le

must be specied in the sendmail.cfle using the option RandFile. It is strongly advised to use

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the "Entropy Gathering Daemon" EGD from Brian Warner on those systems to provide useful

random data. In this case, sendmail must be compiled with the ag EGD, and the RandFile

option must point to the EGD socket. If neither /dev/urandom(4) nor EGD are available, you

have to make sure that useful random data is available all the time in RandFile. If the le hasn’t

been modied in the last 10 minutes before it is supposed to be used by sendmail the content is

considered obsolete. One method for generating this le is:

openssl rand -out /etc/mail/randle -rand /path/to/le:...256

See the OpenSSL documentation for more information. In this case, the PRNG for TLS is only

seeded with other random data if the DontBlameSendmail option InsufcientEntropy is set.

This is most likely not sufcient for certain actions, e.g., generation of (temporary) keys.

Please see the OpenSSL documentation or other sources for further information about cer-

ticates, their creation and their usage, the importance of a good PRNG, and other aspects of

TLS.

6.7. Encoding of STARTTLS and AUTH related Macros

Macros that contain STARTTLS and AUTH related data which comes from outside sources,

e.g., all macros containing information from certicates, are encoded to avoid problems with non-

printable or special characters. The latter are ’\’, ’<’, ’>’, ’(’, ’)’, ’"’, ’+’, and ’ ’. All of these char-

acters are replaced by their value in hexadecimal with a leading ’+’. For example:

/C=US/ST=California/O=endmail.org/OU=private/CN=Darth Mail (Cert)/

Email=darth+cert@endmail.org

is encoded as:

/C=US/ST=California/O=endmail.org/OU=private/

CN=Darth+20Mail+20+28Cert+29/Email=darth+2Bcert@endmail.org

(line breaks have been inserted for readability). The macros which are subject to this encoding are

{cert_subject}, {cert_issuer}, {cn_subject}, {cn_issuer}, as well as {auth_authen} and

{auth_author}.

6.8. DANE

Support for DANE (see RFC 7672 et.al.) is available if sendmail is compiled with the option

DANE. If OpenSSL 1.1.1 or at least 3.0.0 are used, then full DANE support for DANE-EE and

DANE-TA (as required by RFC 7672) is available via the functions provided by those OpenSSL

versions (run

sendmail -bt -d0.3 < /dev/null

and check that HAVE_SSL_CTX_dane_enable is in the output), otherwise support for TLSA RR

3-1-x is implemented directly in sendmail. Note: if OpenSSL functions related to DANE cause a

failure, then the macro ${verify} is set to DANE_TEMP. This also applies if TLS cannot be ini-

tialized at all. The option

O DANE=true

enables this feature at run time and it automatically adds use_dnssec and use_edns0 to

O ResolverOptions

This requires a DNSSEC-validating recursive resolver which supports those options. The resolver

must be reachable via a trusted connection, hence it is best to run it locally.

If the client nds a usable TLSA RR and the check succeeds the macro ${verify} is set to

TRUSTED. All non-DNS maps are considered secure just like DNS lookups with DNSSEC. Be

aw are that TLSA RRs are not looked up for some features, e.g., FallBackSmartHost.

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6.9. EAI

Experimental support for SMTPUTF8 (EAI, see RFC 6530-6533) is available when the com-

pile time option USE_EAI, (see also devtools/Site/site.cong.m4.sample for other settings that

might be needed), and the cf option SMTPUTF8 are used. This allows the use of UTF-8 for

envelope addresses as well as the entire message. DNS lookups are done using the A-label format

(Punycode) as required by the RFCs. For all other interactions with external programs and maps,

the actual value are used, i.e., no conversions between UTF-8 and ASCII encodings are made. This

applies to the keys in map lookups, which might require to specify both versions in a map; the data

exchanged with a milter, i.e., each milter must be "8 bit clean"; mail delivery agents which must be

able to handle 8 bit addresses. Some values must be ASCII as those are used before SMTPUTF8

support can be requested, e.g., the macros $j and $m. Please test and provide feedback.

6.10. MTA-STS

Experimental support for SMTP MTA Strict Transport Security (MTA-STS, see RFC 8461) is

available when using the compile time option _FFR_MTA_STS (as well as some others, e.g.,

_FFR_TLS_ALTNAMES and obviously STARTTLS), FEATURE(sts) (which implicitly sets the cf

option StrictTransportSecurity), and postx-mta-sts-resolver (see https://github.com/Snawoot/post-

x-mta-sts-resolver.git).

Note: this implementation uses a socket map to communicate with postx-mta-sts-resolver

and handles only the values returned by that program, which might not fully implement MTA-STS.

If both DANE and MTA-STS are enabled and available for the receiving domain, DANE is

used because it offers a much higher level of security.

7. ACKNOWLEDGEMENTS

I’ve worked on sendmail for many years, and many employers have been remarkably patient

about letting me work on a large project that was not part of my ofcial job. This includes time on the

INGRES Project at the University of California at Berkeley, at Britton Lee, and again on the Mammoth

and Titan Projects at Berkeley.

Much of the second wav e of improvements resulting in version 8.1 should be credited to Bryan

Costales of the International Computer Science Institute. As he passed me drafts of his book on send-

mail I was inspired to start working on things again. Bryan was also available to bounce ideas off of.

Gregory Neil Shapiro of Worcester Polytechnic Institute has become instrumental in all phases of

sendmail support and development, and was largely responsible for getting versions 8.8 and 8.9 out the

door.

Many, many people contributed chunks of code and ideas to sendmail. It has proven to be a

group network effort. Version 8 in particular was a group project. The following people and organiza-

tions made notable contributions:

Claus Assmann

John Beck, Hewlett-Packard & Sun Microsystems

Keith Bostic, CSRG, University of California, Berkeley

Andrew Cheng, Sun Microsystems

Michael J. Corrigan, University of California, San Diego

Bryan Costales, International Computer Science Institute & InfoBeat

Pa..r (Pell) Emanuelsson

Craig Everhart, Transarc Corporation

Per Hedeland, Ericsson

Tom Ivar Helbekkmo, Norwegian School of Economics

Kari Hurtta, Finnish Meteorological Institute

Allan E. Johannesen, WPI

Jonathan Kamens, OpenVision Technologies, Inc.

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Takahiro Kanbe, Fuji Xerox Information Systems Co., Ltd.

Brian Kantor, University of California, San Diego

John Kennedy, Cal State University, Chico

Murray S. Kucherawy, HookUp Communication Corp.

Bruce Lilly, Sony U.S.

Karl London

Motonori Nakamura, Ritsumeikan University & Kyoto University

John Gardiner Myers, Carnegie Mellon University

Neil Rickert, Northern Illinois University

Gregory Neil Shapiro, WPI

Eric Schnoebelen, Convex Computer Corp.

Eric Wassenaar, National Institute for Nuclear and High Energy Physics, Amsterdam

Randall Winchester, University of Maryland

Christophe Wolfhugel, Pasteur Institute & Herve Schauer Consultants (Paris)

Exactis.com, Inc.

I apologize for anyone I have omitted, misspelled, misattributed, or otherwise missed. At this point, I

suspect that at least a hundred people have contributed code, and many more have contributed ideas,

comments, and encouragement. I’ve tried to list them in the RELEASE_NOTES in the distribution

directory. I appreciate their contribution as well.

Special thanks are reserved for Michael Corrigan and Christophe Wolfhugel, who besides being

wonderful guinea pigs and contributors have also consented to be added to the ‘‘sendmail@Send-

mail.ORG’’ list and, by answering the bulk of the questions sent to that list, have freed me up to do

other work.

APPENDIX A

COMMAND LINE FLAGS

Arguments must be presented with ags before addresses. The ags are:

Ax

Select an alternative .cf le which is either sendmail.cf forAm or submit.cf forAc. By

default the .cf le is chosen based on the operation mode. For -bm (default), -bs, and -t it

is submit.cf if it exists, for all others it is sendmail.cf.

bx

Set operation mode to x. Operation modes are:

m

Deliver mail (default)

s

Speak SMTP on input side

a†

‘‘Arpanet’’ mode (get envelope sender information from header)

C

Check the conguration le

d

Run as a daemon in background

D

Run as a daemon in foreground

t

Run in test mode

v

Just verify addresses, don’t collect or deliver

i

Initialize the alias database

p

Print the mail queue

P

Print overview over the mail queue (requires shared memory)

h

Print the persistent host status database

H

Purge expired entries from the persistent host status database

Btype

Indicate body type.

Cle

Use a different conguration le. Sendmail runs as the invoking user (rather than root)

when this ag is specied.

D logle

Send debugging output to the indicated logle instead of stdout.

dlevel

Set debugging level.

f addr

The envelope sender address is set to addr. This address may also be used in the From:

header if that header is missing during initial submission. The envelope sender address is

used as the recipient for delivery status notications and may also appear in a Return-

Path: header.

F name

Sets the full name of this user to name.

G

When accepting messages via the command line, indicate that they are for relay (gate-

way) submission. sendmail may complain about syntactically invalid messages, e.g.,

unqualied host names, rather than xing them when this ag is set. sendmail will not do

any canonicalization in this mode.

h cnt

Sets the “hop count” to cnt. This represents the number of times this message has been

processed by sendmail (to the extent that it is supported by the underlying networks). Cnt

is incremented during processing, and if it reaches MAXHOP (currently 25) sendmail

throws away the message with an error.

†Deprecated.

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L tag

Sets the identier used for syslog. Note that this identier is set as early as possible.

However, sendmail may be used if problems arise before the command line arguments are

processed.

n

Don’t do aliasing or forwarding.

N notications Tag all addresses being sent as wanting the indicated notications, which consists of the

word “NEVER” or a comma-separated list of “SUCCESS”, “FAILURE”, and “DELAY”

for successful delivery, failure, and a message that is stuck in a queue somewhere. The

default is “FAILURE,DELAY”.

r addr

An obsolete form off.

ox value

Set option x to the specied value. These options are described in Section 5.6.

Ooption=value Set option to the specied value (for long form option names). These options are

described in Section 5.6.

Mx value

Set macro x to the specied value.

pprotocol

Set the sending protocol. Programs are encouraged to set this. The protocol eld can be

in the form protocol:host to set both the sending protocol and sending host. For example,

pUUCP:uunet” sets the sending protocol to UUCP and the sending host to uunet.

(Some existing programs use oM to set the r and s macros; this is equivalent to using

p.)

qtime

Try to process the queued up mail. If the time is given, sendmail will start one or more

processes to run through the queue(s) at the specied time interval to deliver queued mail;

otherwise, it only runs once. Each of these processes acts on a workgroup. These pro-

cesses are also known as workgroup processes or WGP’s for short. Each workgroup is

responsible for controlling the processing of one or more queues; workgroups help man-

age the use of system resources by sendmail. Each workgroup may have one or more

children concurrently processing queues depending on the setting of MaxQueueChildren.

qptime

Similar to q with a time argument, except that instead of periodically starting WGP’s

sendmail starts persistent WGP’s that alternate between processing queues and sleeping.

The sleep time is specied by the time argument; it defaults to 1 second, except that a

WGP always sleeps at least 5 seconds if their queues were empty in the previous run.

Persistent processes are managed by a queue control process (QCP). The QCP is the par-

ent process of the WGP’s. Typically the QCP will be the sendmail daemon (when started

with bd or bD) or a special process (named Queue control) (when started without bd

or bD). If a persistent WGP ceases to be active for some reason another WGP will be

started by the QCP for the same workgroup in most cases. When a persistent WGP has

core dumped, the debug ag no_persistent_restart is set or the specic persistent WGP

has been restarted too many times already then the WGP will not be started again and a

message will be logged to this effect. To stop (SIGTERM) or restart (SIGHUP) persis-

tent WGP’s the appropriate signal should be sent to the QCP. The QCP will propagate the

signal to all of the WGP’s and if appropriate restart the persistent WGP’s.

qGname

Run the jobs in the queue group name once.

q[!]Xstring

Run the queue once, limiting the jobs to those matching Xstring. The key letter X can be

I to limit based on queue identier, R to limit based on recipient, S to limit based on

sender, or Q to limit based on quarantine reason for quarantined jobs. A particular

queued job is accepted if one of the corresponding attributes contains the indicated string.

The optional ! character negates the condition tested. MultipleqXags are permitted,

with items with the same key letter “or’ed” together, and items with different key letters

“and’ed” together.

Q[reason]

Quarantine normal queue items with the given reason or unquarantine quarantined queue

items if no reason is given. This should only be used with some sort of item matching

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usingq[!]Xstring as described above.

R ret

What information you want returned if the message bounces; ret can be “HDRS” for

headers only or “FULL” for headers plus body. This is a request only; the other end is

not required to honor the parameter. If “HDRS” is specied local bounces also return

only the headers.

t

Read the header for “To:”, “Cc:”, and “Bcc:” lines, and send to everyone listed in those

lists. The “Bcc:” line will be deleted before sending. Any addresses in the argument vec-

tor will be deleted from the send list.

U

This option is required when sending mail using UTF-8; it sets the “SMTPUTF8” argu-

ment for “MAIL” command. Only available if “EAI” support is enabled, and the “SMT-

PUTF8” option is set.

V envid

The indicated envid is passed with the envelope of the message and returned if the mes-

sage bounces.

X logle

Log all trafc in and out of sendmail in the indicated logle for debugging mailer prob-

lems. This produces a lot of data very quickly and should be used sparingly.

There are a number of options that may be specied as primitive ags. These are the e, i, m, and v

options. Also, the f option may be specied as thesag. The DSN related options “N”, “R”, and

V” have no effects on sendmail running as daemon.

APPENDIX B

QUEUE FILE FORMATS

This appendix describes the format of the queue les. These les live in a queue directory. The indi-

vidual qf, hf, Qf, df, and xf les may be stored in separate qf/, df/, and xf/ subdirectories if they are present

in the queue directory.

All queue les have the name ttYMDhmsNNppppp where YMDhmsNNppppp is the id for this mes-

sage and the tt is a type. The individual letters in the id are:

Y

Encoded year

M

Encoded month

D

Encoded day

h

Encoded hour

m

Encoded minute

s

Encoded second

NN

Encoded envelope number

ppppp

At least ve decimal digits of the process ID

All les with the same id collectively dene one message. Due to the use of memory-buffered les,

some of these les may never appear on disk.

The types are:

qf

The queue control le. This le contains the information necessary to process the job.

hf

The same as a queue control le, but for a quarantined queue job.

df

The data le. The message body (excluding the header) is kept in this le. Sometimes the df le

is not stored in the same directory as the qf le; in this case, the qf le contains a ‘d’ record which

names the queue directory that contains the df le.

tf

A temporary le. This is an image of the qfle when it is being rebuilt. It should be renamed to a

qfle very quickly.

xf

A transcript le, existing during the life of a session showing everything that happens during that

session. Sometimes the xf le must be generated before a queue group has been selected; in this

case, the xf le will be stored in a directory of the default queue group.

Qf

A ‘‘lost’’ queue control le. sendmail renames a qfle to Qf if there is a severe (conguration)

problem that cannot be solved without human intervention. Search the logle for the queue le id

to gure out what happened. After you resolved the problem, you can rename the Qfle to qf and

send it again.

The queue control le is structured as a series of lines each beginning with a code letter; the le must

end with a line containing only a single dot. The lines are as follows:

V

The version number of the queue le format, used to allow new sendmail binaries to read queue

les created by older versions. Defaults to version zero. Must be the rst line of the le if present.

For 8.13 and later the version number is 8.

A

The information given by the AUTH= parameter of the SMTP MAIL command or $f@$j if send-

mail has been called directly.

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H

A header denition. There may be any number of these lines. The order is important: they repre-

sent the order in the nal message. These use the same syntax as header denitions in the congu-

ration le.

C

The controlling address. The syntax is “localuser:aliasname”. Recipient addresses following this

line will be agged so that deliveries will be run as the localuser (a user name from the

/etc/passwd le); aliasname is the name of the alias that expanded to this address (used for print-

ing messages).

q

The quarantine reason for quarantined queue items.

Q

The ‘‘original recipient’’, specied by the ORCPT= eld in an ESMTP transaction. Used exclu-

sively for Delivery Status Notications. It applies only to the following ‘R’ line.

r

The ‘‘nal recipient’’ used for Delivery Status Notications. It applies only to the following ‘R’

line.

R

A recipient address. This will normally be completely aliased, but is actually realiased when the

job is processed. There will be one line for each recipient. Version 1 qf les also include a lead-

ing colon-terminated list of ags, some of which are ‘S’ to return a message on successful nal

delivery, ‘F’ to return a message on failure, ‘D’ to return a message if the message is delayed, ‘N’

to suppress returning the body, and ‘P’ to declare this as a ‘‘primary’’ (command line or SMTP-

session) address.

S

The sender address. There may only be one of these lines.

T

The job creation time. This is used to compute when to time out the job.

P

The current message priority. This is used to order the queue. Higher numbers mean lower priori-

ties. The priority changes as the message sits in the queue. The initial priority depends on the

message class and the size of the message.

M

A message. This line is printed by the mailq command, and is generally used to store status infor-

mation. It can contain any text.

F

Flag bits, represented as one letter per ag. Dened ag bits are r indicating that this is a response

message and w indicating that a warning message has been sent announcing that the mail has been

delayed. Otherag bits are: 8: the body contains 8bit data, b: a Bcc: header should be removed, d:

the mail has RET parameters (see RFC 1894), n: the body of the message should not be returned

in case of an error, s: the envelope has been split.

N

The total number of delivery attempts.

K

The time (as seconds since January 1, 1970) of the last delivery attempt.

d

If the df le is in a different directory than the qf le, then a ‘d’ record is present, specifying the

directory in which the df le resides.

I

The i-number of the data le; this can be used to recover your mail queue after a disastrous disk

crash.

$

A macro denition. The values of certain macros are passed through to the queue run phase.

B

The body type. The remainder of the line is a text string dening the body type. If this eld is

missing, the body type is assumed to be “undened” and no special processing is attempted. Legal

values are “7BIT” and “8BITMIME”.

Z

The original envelope id (from the ESMTP transaction). For Deliver Status Notications only.

!

Information for Deliver-By SMTP extension.

As an example, the following is a queue le sent to “eric@mammoth.Berkeley.EDU” and

SMM:08-114

Sendmail Installation and Operation Guide

“bostic@okeeffe.CS.Berkeley.EDU”1:

V4

T711358135

K904446490

N0

P2100941

$_eric@localhost

${daemon_ags}

Seric

Ceric:100:1000:sendmail@vangogh.CS.Berkeley.EDU

RPFD:eric@mammoth.Berkeley.EDU

RPFD:bostic@okeeffe.CS.Berkeley.EDU

H?P?Return-path: <ˆg>

H??Received: by vangogh.CS.Berkeley.EDU (5.108/2.7) id AAA06703;

Fri, 17 Jul 1992 00:28:55 -0700

H??Received: from mail.CS.Berkeley.EDU by vangogh.CS.Berkeley.EDU (5.108/2.7)

id AAA06698; Fri, 17 Jul 1992 00:28:54 -0700

H??Received: from [128.32.31.21] by mail.CS.Berkeley.EDU (5.96/2.5)

id AA22777; Fri, 17 Jul 1992 03:29:14 -0400

H??Received: by foo.bar.baz.de (5.57/Ultrix3.0-C)

id AA22757; Fri, 17 Jul 1992 09:31:25 GMT

H?F?From: eric@foo.bar.baz.de (Eric Allman)

H?x?Full-name: Eric Allman

H??Message-id: <9207170931.AA22757@foo.bar.baz.de>

H??To: sendmail@vangogh.CS.Berkeley.EDU

H??Subject: this is an example message

.

This shows the person who sent the message, the submission time (in seconds since January 1, 1970), the

message priority, the message class, the recipients, and the headers for the message.

1This example is contrived and probably inaccurate for your environment. Glance over it to get an idea; nothing can replace

looking at what your own system generates.

APPENDIX C

SUMMARY OF SUPPORT FILES

This is a summary of the support les that sendmail creates or generates. Many of these can be

changed by editing the sendmail.cf le; check there to nd the actual pathnames.

/usr/sbin/sendmail

The binary of sendmail.

/usr/bin/newaliases

A link to /usr/sbin/sendmail; causes the alias database to be rebuilt. Running this pro-

gram is completely equivalent to giving sendmail thebiag.

/usr/bin/mailq

Prints a listing of the mail queue. This program is equivalent to using thebpag to

sendmail.

/etc/mail/sendmail.cf

The conguration le, in textual form.

/etc/mail/helple The SMTP help le.

/etc/mail/statistics

A statistics le; need not be present.

/etc/mail/sendmail.pid

Created in daemon mode; it contains the process id of the current SMTP daemon. If you

use this in scripts; use ‘‘head 1’’ to get just the rst line; the second line contains the

command line used to invoke the daemon, and later versions of sendmail may add more

information to subsequent lines.

/etc/mail/aliases The textual version of the alias le.

/etc/mail/aliases.db

The alias le in hash (3) format.

/etc/mail/aliases.{pag,dir}

The alias le in ndbm (3) format.

/var/spool/mqueue

The directory in which the mail queue(s) and temporary les reside.

/var/spool/mqueue/qf*

Control (queue) les for messages.

/var/spool/mqueue/df*

Data les.

/var/spool/mqueue/tf*

Temporary versions of the qf les, used during queue le rebuild.

/var/spool/mqueue/xf*

A transcript of the current session.

Sendmail Installation and Operation Guide

SMM:08-115

SMM:08-116

Sendmail Installation and Operation Guide

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