.he 'Sendmail Installation and Operation Guide''%'
.fo 'Version 4.4''Last Mod %G%'
.b "INSTALLATION AND OPERATION GUIDE"
implements a general purpose internetwork mail routing facility
*UNIX is a trademark of Bell Laboratories.
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.
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 configuration file.
Due to the requirements of flexibility
the configuration file can seem somewhat unapproachable.
However, there are only a few basic configurations
for which standard configuration files have been supplied.
Most other configurations
can be built by adjusting an existing configuration files
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
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 sufficient information
describes some parameters that may be safely tweaked.
has information regarding the command line arguments.
contains the nitty-gritty information about the configuration
This section is for masochists
and people who must write their own configuration file.
The appendixes give a brief
but detailed explanation of a number of features
not described in the rest of the paper.
The references in this paper are actually found
Sendmail \- An Internetwork Mail Router.
This other paper should be read before this manual
to gain a basic understanding
of how the pieces fit together.
.sh 1 "BASIC INSTALLATION"
There are two basic steps to installing sendmail.
The hard part is to build the configuration table.
This is a file that sendmail reads when it starts up
that describes the mailers it knows about,
how to rewrite the message header,
and the settings of various options.
Although the configuration table is quite complex,
a configuration can usually be built
by adjusting an existing off-the-shelf configuration.
The second part is actually doing the installation,
i.e., creating the necessary files, etc.
The remainder of this section will describe the installation of sendmail
assuming you can use one of the existing configurations
and that the standard installation parameters are acceptable.
All pathnames and examples
are given from the root of the
.sh 2 "Off-The-Shelf Configurations"
are all in the subdirectory
of the sendmail directory.
The ones used at Berkeley are in
while files with names ending
processed versions of the corresponding
Two off the shelf configuration files are supplied
to handle the basic cases:
The file you need should be copied to a file with the same name
cp uucpproto.cf ucsfcgl.cf
is now ready for installation as
.i /usr/lib/sendmail.cf .
.sh 2 "Installation Using the Makefile"
A makefile exists in the root of the
directory that will do all of these steps
It may have to be slightly tailored
for use on other systems.
Before using this makefile,
you should already have created your configuration file
is the name of your system
(i.e., what is returned by
you can use the declaration
You should also examine the file
macros there to reflect any libraries and compilation flags
The basic installation procedure is to type:
in the root directory of the
This will make all binaries
and install them in the standard places.
command must be executed as the superuser (root).
.sh 2 "Installation by Hand"
Along with building a configuration file,
you will have to install the
startup into your UNIX system.
If you are doing this installation
in conjunction with a regular Berkeley UNIX install,
these steps will already be complete.
Many of these steps will have to be executed as the superuser (root).
The library in lib/libsys.a
contains some routines that should in some sense
be part of the system library.
These are the system logging routines
and the new directory access routines
If you are not running the new 4.2bsd directory code
and do not have the compatibility routines installed in your system library,
you should execute the commands:
This will compile and install the 4.2 compatibility routines
This will recompile and fill the library.
.sh 3 "/usr/lib/sendmail"
The binary for sendmail is located in /usr/lib.
There is a version available in the source directory
that is probably inadequate for your system.
You should plan on recompiling and installing the entire system:
.sh 3 "/usr/lib/sendmail.cf"
should be installed in /usr/lib/sendmail.cf:
cp cf/\fIsystem\fP.cf /usr/lib/sendmail.cf
.sh 3 "/usr/ucb/newaliases"
If you are running delivermail,
This can just be a link to
rm \-f /usr/ucb/newaliases
ln /usr/lib/sendmail /usr/ucb/newaliases
.sh 3 "/usr/spool/mqueue"
should be created to hold the mail queue.
This directory should be mode 777
should be owned by the sendmail owner
.sh 3 "/usr/lib/aliases*"
The system aliases are held in three files.
which includes some aliases which
cp lib/aliases /usr/lib/aliases
You should extend this file with any aliases that are apropos to your system.
looks at a version of these files maintained by the
These can initially be created as empty files,
but they will have to be initialized promptly.
These should be mode 666 if you are running a reasonably relaxed system:
cp /dev/null /usr/lib/aliases.dir
cp /dev/null /usr/lib/aliases.pag
chmod 666 /usr/lib/aliases.*
.sh 3 "/usr/lib/sendmail.fc"
If you intend to install the frozen version of the configuration file
you should create the file /usr/lib/sendmail.fc
This step may be safely skipped.
cp /dev/null /usr/lib/sendmail.fc
It will be necessary to start up the sendmail daemon when your system reboots.
This daemon 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.
Add the following lines to
in the area where it is starting up the daemons:
if [ \-f /usr/lib/sendmail ]; then
(cd /usr/spool/mqueue; rm \-f [lnx]f*)
/usr/lib/sendmail \-bd \-q30m &
echo \-n ' sendmail' >/dev/console
commands insure that all lock files have been removed;
extraneous lock files may be left around
if the system goes down in the middle of processing a message.
The line that actually invokes
causes it to listen on the SMTP port,
causes it to run the queue every half hour.
If you are not running a version of UNIX
that supports Berkeley TCP/IP,
.sh 3 "/usr/lib/sendmail.hf"
This is the help file used by the SMTP
cp lib/sendmail.hf /usr/lib
.sh 3 "/usr/lib/sendmail.st"
If you wish to collect statistics
you should create the file
.q /usr/lib/sendmail.st :
cp /dev/null /usr/lib/sendmail.st
chmod 666 /usr/lib/sendmail.st
It is printed with the program
(to collect log information about sendmail).
This program normally resides in
The program is located in the
describes the file(s) that sendmail will log in.
For a complete description of syslog,
.sh 3 "/usr/ucb/newaliases"
(i.e., will rebuild the alias database;
This should be a link to /usr/lib/sendmail.
will print the contents of the mail queue;
This should be a link to /usr/lib/sendmail.
.sh 1 "NORMAL OPERATIONS"
.sh 2 "Quick Configuration Startup"
A fast version of the configuration file
may be set up by using the
.q "frozen configuration" ).
data space after reading in the configuration file.
must be rebuilt manually every time
The frozen configuration file will be ignored
or if sendmail detects that it is out of date.
However, the heuristics are not strong
so this should not be trusted.
The system log is supported by the
Each line in the system log
the name of the machine that generated it
(for logging from several machines
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.
only extremely strange situations are logged.
even the most mundane and uninteresting events
are recorded for posterity.
are usually for debugging purposes.
A complete description of the log levels
The mail queue should be processed transparently.
However, you may find that manual intervention is sometimes necessary.
if a major host is down for a period of time
the queue may become clogged.
Although sendmail ought to recover gracefully when the host comes up,
you may find performance unacceptably bad in the meantime.
.sh 3 "Printing the queue"
The contents of the queue can be printed
This will produce a listing of the queue id's,
the date the message entered the queue,
and the sender and recipients.
.sh 3 "Format of queue files"
All queue files have the form
\fIx\fP\|\fBf\fP\fIAA99999\fP
The message body (excluding the header) is kept in this file.
the job is currently being processed,
and a queue run will not process the file.
file can cause a job to apparently disappear
(it will not even time out!).
This file is created when an id is being created.
It is a separate file to insure that no mail can ever be destroyed
It should exist for no more than a few milliseconds
This file contains the information necessary to process the job.
These are an image of the
file when it is being rebuilt.
It should be renamed to a
existing during the life of a session
showing everything that happens
file is structured as a series of lines
each beginning with a code letter.
The lines are as follows:
The name of the data file.
There may only be one of these lines.
There may be any number of these lines.
they represent the order in the final message.
These use the same syntax
as header definitions in the configuration file.
This will normally be completely aliased,
but is actually realiased when the job is processed.
There may only be one of these lines.
This is used to compute when to time out the job.
The current message priority.
This is used to order the queue.
Higher numbers mean lower priorities.
as the message sits in the queue.
The initial priority depends on the message class
and the size of the message.
This line is printed by the
and is generally used to store status information.
the following is a queue file sent to
H?D?date: 23-Oct-82 15:49:32-PDT (Sat)
H?F?from: eric (Eric Allman)
H?x?full-name: Eric Allman
Hsubject: this is an example message
Hmessage-id: <8209232249.13557@UCBARPA.BERKELEY.ARPA>
Hreceived: by UCBARPA.BERKELEY.ARPA (3.227 [10/22/82])
id A13557; 23-Oct-82 15:49:32-PDT (Sat)
HTo: mckusick@calder, wnj
This shows the name of the data file,
the person who sent the message,
(in seconds since January 1, 1970),
and the headers for the message.
.sh 3 "Forcing the queue"
should run the queue automatically
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,
first 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
since there is no guarantee that a job cannot take forever
Due to the locking algorithm,
it is impossible for one job to freeze the queue.
an uncooperative recipient host
can accumulate many processes in your system.
there is no way to resolve this
without violating the protocol.
you may find that a major host going down
may create a prohibitively large queue.
spending an inordinate amount of time
This situation can be fixed 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.
it is acceptable to move the entire queue directory:
mv mqueue omqueue; mkdir mqueue; chmod 777 mqueue
You should then kill the existing daemon
(since it will still be processing in the old queue directory)
To run the old mail queue,
run the following command:
/usr/lib/sendmail \-oQ/usr/spool/omqueue \-q
flag specifies an alternate queue directory
flag says to just run every job in the queue.
If you have a tendency toward voyeurism,
flag to watch what is going on.
When the queue is finally emptied,
you can remove the directory:
.sh 2 "The Alias Database"
The alias database exists in two forms.
The aliases are of the form
Only local names may be aliased;
eric@mit-xx: eric@berkeley
will not have the desired effect.
Aliases may be continued by starting any continuation lines
Blank lines and lines beginning with a sharp sign
The second form is processed by the
This form is in the files
actually uses to resolve aliases.
This technique is used to improve performance.
.sh 3 "Rebuilding the alias database"
The DBM version of the database
may be rebuilt explicitly by executing the command
This is equivalent to giving
option is specified in the configuration,
will rebuild the alias database automatically
The conditions under which it will do this are:
The DBM version of the database is mode 666. -or-
is running setuid to root.
Auto-rebuild can be dangerous
on heavily loaded machines
if it might take more than five minutes
there is a chance that several processes will start the rebuild process
.sh 3 "Potential problems"
There are a number of problems that can occur
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 two 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.
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 exists\**.
option is required in the configuration
for this action to occur.
This should normally be specified
will wait for this entry to appear,
at which point it will force a rebuild itself\**.
option must be specified in the configuration file
for this operation to occur.
a warning message is generated and
If an error occurs on sending to a certain address,
where the submitter of the list
has no control over the maintanence of the list itself;
in this case the list maintainer would be the owner of the list.
unix-wizards: eric@ucbarpa, wnj@monet, nosuchuser,
owner-unix-wizards: eric@ucbarpa
to get the error that will occur
.sh 2 "Per-User Forwarding (.forward Files)"
As an alternative to the alias database,
any user may put a file with the name
in his or her home directory.
redirects mail for that user
to the list of addresses listed in the .forward file.
For example, if the home directory for user
has a .forward file with contents:
then any mail arriving for
will be redirected to the specified accounts.
.sh 2 "Special Header Lines"
Several header lines have special interpretations
defined by the configuration file.
Others have interpretations built into
that cannot be changed without changing the code.
These builtins are described here.
.sh 3 "Return-Receipt-To:"
a message will be sent to any specified addresses
when the final delivery is complete.
flag (local delivery) set in the mailer descriptor.
If errors occur anywhere during processing,
this header will cause error messages to go to
rather than to the sender.
This is intended for mailing lists.
If a message comes in with no recipients listed in the message
(in a To:, Cc:, or Bcc: line)
header line for any recipients it is aware of.
This is not put in as a standard recipient line
to warn any recipients that the list is not complete.
At least one recipient line is required under RFC 822.
The complete list of arguments to
is described in detail in Appendix A.
Some important arguments are described here.
The amount of time between forking a process
this can be relatively large,
since it will only be relevant
when a host that was down comes back up.
it should be relatively short,
since it defines the maximum amount of time that a message
If you allow incoming mail over an IPC connection,
you should have a daemon running.
This should be set by your
flag may be combined in one call:
/usr/lib/sendmail \-bd \-q30m
.sh 2 "Forcing the Queue"
In some cases you may find that the queue has gotten clogged for some reason.
You can force a queue run
It is entertaining to use the
when this is done to watch what happens:
/usr/lib/sendmail \-q \-v
There are a fairly large number of debug flags
Each debug flag has a number and a level,
where higher levels means to print out more information.
The convention is that levels greater than nine are
they print out so much information that you wouldn't normally
want to see them except for debugging that particular piece of code.
Debug flags are set using the
debug-flag: \fB\-d\fP debug-list
debug-list: debug-option [ , debug-option ]
debug-option: debug-range [ . debug-level ]
debug-range: integer | integer \- integer
where spaces are for reading ease only.
\-d12 Set flag 12 to level 1
\-d12.3 Set flag 12 to level 3
\-d3-17 Set flags 3 through 17 to level 1
\-d3-17.4 Set flags 3 through 17 to level 4
For a complete list of the available debug flags
you will have to look at the code
(they are too dynamic to keep this documentation up to date).
.sh 2 "Trying a Different Configuration File"
An alternative configuration file
can be specified using the
/usr/lib/sendmail \-Ctest.cf
uses the configuration file
in the current directory.
.sh 2 "Changing the Values of Options"
Options can be overridden using the
(timeout) option to two minutes
There are a number of configuration parameters
depending on the requirements of your site.
using an option in the configuration file.
All time intervals are set
represents ten minutes, whereas
represents two and a half hours.
The full set of scales is:
specifies how often a subdaemon will run the queue.
This is typically set to between five minutes
It is possible to time out when reading the standard input
or when reading from a remote SMTP server.
this is not acceptable within the published protocols.
it might be appropriate to set it to something large
This will reduce the chance of large numbers of idle daemons
piling up on your system.
This timeout is set using the
option in the configuration file.
After sitting in the queue for a few days,
This is to insure that at least the sender is aware
of the inability to send a message.
The timeout is typically set to three days.
This timeout is set using the
option in the configuration file.
The time of submission is set in the queue,
rather than the amount of time left until timeout.
As a result, you can flush messages that have been hanging
with a short message timeout.
/usr/lib/sendmail \-oT1d \-q
and flush anything that is one day old.
There are a number of delivery modes that
specify how quickly mail will be delivered.
i deliver interactively (synchronously)
b deliver in background (asynchronously)
q queue only (don't deliver)
passes the maximum amount of information to the sender,
but is hardly ever necessary.
puts the minimum load on your machine,
but means that delivery may be delayed for up to the queue interval.
is probably a good compromise.
However, this mode can cause large numbers of processes
if you have a mailer that takes a long time to deliver a message.
The level of logging can be set for sendmail.
The default using a standard configuration table is level 9.
The levels are as follows:
Message collections and failed deliveries.
(due to a host being down, etc.).
Unusual but benign incidents,
trying to process a locked queue file.
Log internal queue id to external message id mappings.
This can be useful for tracing a message
as it travels between several hosts.
Several messages that are basically only of interest
Verbose information regarding the queue.
can be asked to queue (but not deliver)
mail if the system load average gets too high
When the load average exceeds the value of the
the delivery mode is set to
option defines a load average at which sendmail will refuse
to connect network connections.
(including incoming UUCP mail)
There are a number of files
that may have a number of modes.
The modes depend on what functionality you want
and the level of security you require.
.sh 3 "To suid or not to suid?"
At the point where it is about to
it checks to see if the userid is zero;
it resets the userid and groupid to a default
for mailers that are trusted
and must be called as root.)
this will cause mail processing
rather than to the user sending the mail.
.sh 3 "Temporary file modes"
The mode of all temporary files that
creates is determined by the
Reasonable values for this option are
If the more permissive mode is selected,
it will not be necessary to run
(even when running the queue).
.sh 3 "Should my alias database be writable?"
we have the alias database
There are some dangers inherent in this approach:
any user can add him-/her-self
we have found users to be basically trustworthy,
and the cost of having a read-only database
greater than the expense of finding and eradicating
is represented by the two files
The mode on these files should match the mode
users will be unable to reflect their desired changes
through to the actual database.
and the DBM files are writable,
a slightly sophisticated user
can arrange to steal mail anyway.
If your DBM files are not writable by the world
or you do not have auto-rebuild enabled
then you must be careful to reconstruct the alias database
each time you change the text version:
If this step is ignored or forgotten
any intended changes will also be ignored or forgotten.
.sh 1 "THE WHOLE SCOOP ON THE CONFIGURATION FILE"
This section describes the configuration file
including hints on how to write one of your own
There is one point that should be made clear immediately:
the syntax of the configuration file
is designed to be reasonably easy to parse,
since this is done every time
rather than easy for a human to read or write.
configuration-file compiler.
An overview of the configuration file
followed by details of the semantics.
The configuration file is organized as a series of lines,
each of which begins with a single character
defining the semantics for the rest of the line.
Lines beginning with a space or a tab
(although the semantics are not well defined in many places).
Blank lines and lines beginning with a sharp symbol
.sh 3 "R and S \*- rewriting rules"
The core of address parsing
These are an ordered production system.
scans through the set of rewriting rules
looking for a match on the left hand side
the address is replaced by the right hand side
There are several sets of rewriting rules.
Some of the rewriting sets are used internally
and must have specific semantics.
do not have specifically assigned semantics,
and may be referenced by the mailer definitions
or by other rewriting sets.
The syntax of these two commands are:
Sets the current ruleset being collected to
If you begin a ruleset more than once
it deletes the old definition.
by at least one tab character;
there may be embedded spaces
is a pattern that is applied to the input.
the input is rewritten to the
.sh 3 "D \*- define macro"
Macros are named with a single character.
These may be selected from the entire ASCII set,
should be selected from the set of upper case letters only.
The syntax for macro definitions is:
is the value it should have.
Macros can be interpolated in most places using the escape sequence
.sh 3 "C and F \*- define classes"
Classes of words may be defined
to match on the left hand side of rewriting rules.
a class of all local names for this site
so that attempts to send to oneself
These can either be defined directly in the configuration file
or read in from another file.
Classes may be given names
from the set of upper case letters.
Lower case letters and special characters
are reserved for system use.
The first form defines the class
to match any of the named words.
It is permissible to split them among multiple lines;
for example, the two forms:
reads the elements of the class
that should produce a single string.
.sh 3 "M \*- define mailer"
Programs and interfaces to mailers
are defined in this line.
is the name of the mailer
pairs define attributes of the mailer.
Path The pathname of the mailer
Flags Special flags for this mailer
Sender A rewriting set for sender addresses
Recipient A rewriting set for recipient addresses
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
Only the first character of the field name is checked.
.sh 3 "H \*- define header"
The format of the header lines that sendmail inserts into the message
The syntax of this line is:
Continuation lines in this spec
are reflected directly into the outgoing message.
is macro expanded before insertion into the message.
(surrounded by question marks)
at least one of the specified flags
must be stated in the mailer definition
for this header to be automatically output.
If one of these headers is in the input
it is reflected to the output
regardless of these flags.
Some headers have special semantics
that will be described below.
can be set from a configuration file.
Options are represented by single characters.
The syntax of this line is:
may be a string, an integer,
.sh 3 "T \*- define trusted users"
are those users who are permitted
to override the sender address
but on some users it may be convenient
to extend this list to include other users,
The syntax of this line is:
There may be more than one of these lines.
.sh 3 "P \*- precedence definitions"
field may be defined using the
The syntax of this field is:
\fBP\fP\fIname\fP\fB=\fP\fInum\fP
the message class is set to
Higher numbers mean higher precedence.
have the special property
that error messages will not be returned.
The default precedence is zero.
our list of precedences is:
This section describes the semantics of the configuration file.
.sh 3 "Special macros, conditionals"
is the name of the macro to be interpolated.
lower case letters are reserved to have
used to pass information in or out of sendmail,
and some special characters are reserved to
provide conditionals, etc.
be defined to transmit information into
j The \*(lqofficial\*(rq domain name for this site
l The format of the UNIX from line
n The name of the daemon (for error messages)
o The set of "operators" in addresses
q default format of sender address
macro is printed out when SMTP starts up.
The first word must be the
should be in RFC821 format.
macros can be considered constants
except under terribly unusual circumstances.
macro consists of a list of characters
which will be considered tokens
and which will separate tokens
would be scanned as three tokens:
macro specifies how an address should appear in a message
For example, on our system these definitions are:
De$j Sendmail $v ready at $b
An acceptable alternative for the
These correspond to the following two formats:
eric@Berkeley (Eric Allman)
Eric Allman <eric@Berkeley>
Some macros are defined by
for interpolation into argv's for mailers
a The origination date in Arpanet format
b The current date in Arpanet format
d The date in UNIX (ctime) format
f The sender (from) address
g The sender address relative to the recipient
t A numeric representation of the current time
v The version number of sendmail
w The hostname of this site
x The full name of the sender
z The home directory of the recipient
There are three types of dates that can be used.
macros are in Arpanet format;
is the time as extracted from the
is the current date and time
line is found in the incoming message,
is set to the current time also.
macro is equivalent to the
macro is the id of the sender
as originally determined;
when mailing to a specific host
macro is set to the address of the sender
relative to the recipient.
macro is set to the full name of the sender.
This can be determined in several ways.
It can be passed as flag to
The second choice is the value of the
line in the header if it exists,
and the third choice is the comment field
and if the message is being originated locally,
the full name is looked up in the
macros get set to the host, user, and home directory
The first two are set from the
part of the rewriting rules, respectively.
macros are used to create unique strings
macro is set to the queue id on this host;
if put into the timestamp line
it can be extremely useful for tracking messages.
macro is set to be the version number of
this is normally put in timestamps
and has been proven extremely useful for debugging.
macro is set to the name of this host
i.e., the number of times this message has been processed.
or by counting the timestamps in the message.
fields are set to the protocol used to communicate with sendmail
and the sending hostname;
these are not supported in the current version.
Conditionals can be specified using the syntax:
is set to be the set of all names
This can be used to delete local hostnames.
.sh 3 "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.
.ta \w'\fB$=\fP\fIx\fP 'u
\fB$*\fP Match zero or more tokens
\fB$+\fP Match one or more tokens
\fB$\-\fP Match exactly one token
\fB$=\fP\fIx\fP Match any token in class \fIx\fP
\fB$~\fP\fIx\fP Match any token not in class \fIx\fP
they are assigned to the symbol
for replacement on the right hand side,
the rule will match, and the values passed to the RHS will be:
.sh 3 "The right hand side"
When the left hand side of a rewriting rule matches,
the input is deleted and replaced by the right hand side.
Tokens are copied directly from the RHS
unless they are begin with a dollar sign.
\fB$\fP\fIn\fP Substitute indefinite token \fIn\fP from LHS
\fB$[\fP\fIname\fP\fB$]\fP Canonicalize \fIname\fP
\fB$>\fP\fIn\fP \*(lqCall\*(rq ruleset \fIn\fP
\fB$#\fP\fImailer\fP Resolve to \fImailer\fP
\fB$@\fP\fIhost\fP Specify \fIhost\fP
\fB$:\fP\fIuser\fP Specify \fIuser\fP
syntax substitutes the corresponding value from a
A host name enclosed between
file and replaced by the canonical name.
causes the remainder of the line to be substituted as usual
and then passed as the argument to ruleset
The final value of ruleset
the substitution for this rule.
It causes evaluation of the ruleset to terminate immediately,
and signals to sendmail that the address has completely resolved.
\fB$#\fP\fImailer\fP\fB$@\fP\fIhost\fP\fB$:\fP\fIuser\fP
3-tuple necessary to direct the mailer.
the host part may be omitted.
A RHS may also be preceeded by a
prefix causes the ruleset to return with the remainder of the RHS
prefix causes the rule to terminate immediately,
but the ruleset to continue;
this can be used to avoid continued application of a rule.
The prefix is stripped before continuing.
passes that to ruleset seven,
is necessary to avoid an infinite loop.
Substitution occurs in the order described,
parameters from the LHS are substituted,
hostnames are canonicalized,
.sh 3 "Semantics of rewriting rule sets"
There are five rewriting sets
that have specific semantics.
These are related as depicted by figure 2.
-->| 0 |-->resolved address
+---+ / +---+ / +---+ +---+ \e +---+
addr-->| 3 |-->| D |-- --->| 4 |-->msg
+---+ +---+ \e +---+ +---+ / +---+
Figure 2 \*- Rewriting set semantics
D \*- sender domain addition
S \*- mailer-specific sender rewriting
R \*- mailer-specific recipient rewriting
should turn the address into
This form should have the basic syntax:
local-part@host-domain-spec
flag is set in the mailer definition
before doing anything with any address.
is applied after ruleset three
to addresses that are going to actually specify recipients.
.i "{mailer, host, user}"
must be defined in the mailer definitions
from the configuration file.
for use in the argv expansion of the specified mailer.
are applied to all sender and recipient addresses respectively.
They are applied before any specification
in the mailer definition.
Ruleset four is applied to all addresses
to translate internal to external form.
.sh 3 "Mailer flags etc."
There are a number of flags that may be associated with each mailer,
each identified by a letter of the alphabet.
Many of them are assigned semantics internally.
These are detailed in Appendix C.
Any other flags may be used freely
to conditionally assign headers to messages
destined for particular mailers.
.sh 3 "The \*(lqerror\*(rq mailer"
The mailer with the special name
can be used to generate a user error.
The (optional) host field is a numeric exit status to be returned,
and the user field is a message to be printed.
$#error$:Host unknown in this domain
will cause the specified error to be generated
This mailer is only functional in ruleset zero.
.sh 2 "Building a Configuration File From Scratch"
Building a configuration table from scratch is an extremely difficult job.
it is almost never necessary to do so;
nearly every situation that may come up
may be resolved by changing an existing table.
it is critical that you understand what it is that you are trying to do
and come up with a philosophy for the configuration table.
This section is intended to explain what the real purpose
of a configuration table is
and to give you some ideas
for what your philosophy might be.
.sh 3 "What you are trying to do"
The configuration table has three major purposes.
is to set up the environment for
This involves setting the options,
defining a few critical macros,
Since these are described in other places,
we will not go into more detail here.
The second purpose is to rewrite addresses in the message.
This should typically be done in two phases.
The first phase maps addresses in any format
This should be done in ruleset three.
The second phase maps this canonical form
into the syntax appropriate for the receiving mailer.
does this in three subphases.
are applied to all sender and recipient addresses respectively.
you may specify per-mailer rulesets
for both sender and recipient addresses;
this allows mailer-specific customization.
ruleset four is applied to do any default conversion
is to map addresses into the actual set of instructions
necessary to get the message delivered.
Ruleset zero must resolve to the internal form,
which is in turn used as a pointer to a mailer descriptor.
The mailer descriptor describes the interface requirements
The particular philosophy you choose will depend heavily
on the size and structure of your organization.
I will present a few possible philosophies here.
One general point applies to all of these philosophies:
it is almost always a mistake
to try to do full name resolution.
if you are trying to get names of the form
it does not pay to route them to
.q xyzvax!decvax!ucbvax!c70:user@host
since you then depend on several links not under your control.
The best approach to this problem
worry about it from there.
just get the message closer to the destination,
rather than determining the full path.
.sh 4 "Large site, many hosts \*- minimum information"
Berkeley is an example of a large site,
i.e., more than two or three hosts.
We have decided that the only reasonable philosophy
is to designate one host as the guru for our site.
It must be able to resolve any piece of mail it receives.
The other sites should have the minimum amount of information
any information they do have
should be hints rather than solid information.
a typical site on our local ether network is
Monet has a list of known ethernet hosts;
if it receives mail for any of them,
it can do direct delivery.
If it receives mail for any unknown host,
it just passes it directly to
Ucbvax may determine that the host name is illegal
or may be able to do delivery.
However, it is important to note that when a new ethernet host is added,
be updated as convenient,
but this is not critical.
This picture is slightly muddied
due to network connections that are not actually located
our TCP connection is currently on
the information is hidden totally between ucbvax and ucbarpa.
Mail going from monet to a TCP host
is transfered via the ethernet
then via the ethernet from ucbvax to ucbarpa,
and then is submitted to the Arpanet.
Although this involves some extra hops,
we feel this is an acceptable tradeoff.
An interesting point is that it would be possible
to send TCP mail directly to ucbarpa
if the load got too high;
if monet failed to note a host as a TCP host
it would go via ucbvax as before,
and if monet incorrectly sent a message to ucbarpa
it would still be sent by ucbarpa
The only problem that can occur is loops,
as if ucbarpa thought that ucbvax had the TCP connection
happen to the master host first.
This philosophy results as much from the need
to have a single source for the configuration files
Maintaining more than three separate tables by hand
is essentially an impossible job.
.sh 4 "Small site \*- complete information"
may find it more reasonable to have complete information
This would require that each host
know exactly where each network connection is,
possibly including the names of each host on that network.
As long as the site remains small
and the the configuration remains relatively static,
the update problem will probably not be too great.
This is in some sense the trivial case.
The only major issue is trying to insure that you don't
have to know too much about your environment.
if you have a UUCP connection
you might find it useful to know about the names of hosts
connected directly to you,
but this is really not necessary
since this may be determined from the syntax.
The canonical form you use
should almost certainly be as specified in
Copies of these RFC's are included on the
describes the format of the mail message itself.
follows this RFC closely,
to the extent that many of the standards described in this document
can not be changed without changing the code.
the following characters have special interpretations:
Any attempt to use these characters for other than their RFC822
purpose in addresses is probably doomed to disaster.
describes the specifics of the domain-based addressing.
This is touched on in RFC822 as well.
Essentially each host is given a name
which is a right-to-left dot qualified pseudo-path
from a distinguished root.
The elements of the path need not be physical hosts;
the domain is logical rather than physical.
reading from right to left,
(related to, but not limited to, the physical Arpanet),
is both an Arpanet host and a logical domain
which is actually interpreted by
(which is actually just the
represents the Computer Center,
(in this case a strictly logical entity),
is a host in the Computer Center;
this particular host happens to be connected
but other hosts might be connected via one of two ethernets
Beware when reading RFC819
that there are a number of errors in it.
Once you have decided on a philosophy,
it is worth examining the available configuration tables
to decide if any of them are close enough
Even under the worst of conditions,
there is a fair amount of boiler plate that can be collected safely.
The next step is to build ruleset three.
This will be the hardest part of the job.
Beware of doing too much to the address in this ruleset,
since anything you do will reflect through
stripping of local domains is best deferred,
since this can leave you with addresses with no domain spec at all.
likes to append the sending domain to addresses with no domain,
this can change the semantics of addresses.
fully qualifying domains in this ruleset.
Although technically legal,
this can lead to unpleasantly and unnecessarily long addresses
The Berkeley configuration files
to qualify domain names and strip local domains.
This is called from ruleset zero
to get all addresses into a cleaner form.
Once you have ruleset three finished,
the other rulesets should be relatively trivial.
examine the supplied configuration tables.
.sh 3 "Testing the rewriting rules \*- the \-bt flag"
When you build a configuration table,
you can do a certain amount of testing
which would read the configuration file
you enter lines of the form:
is the rewriting set you want to use
is an address to apply the set to.
Test mode shows you the steps it takes
finally 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;
ruleset three is always applied first.
first applies ruleset three to the input
Ruleset one is then applied to the output of ruleset three,
followed similarly by rulesets twenty-one and four.
flag to turn on more debugging.
turns on an incredible amount of information;
is probably going to print out several pages worth of information.
.sh 3 "Building mailer descriptions"
To add an outgoing mailer to your mail system,
you will have to define the characteristics of the mailer.
Each mailer must have an internal name.
The pathname of the mailer must be given in the P field.
If this mailer should be accessed via an IPC connection,
The F field defines the mailer flags.
flag to pass the name of the sender as a
These flags are only passed if they were passed to
so that mailers that give errors under some circumstances
If the mailer is not picky
If the mailer must be called as
this will not reset the userid
before calling the mailer\**.
must be running setuid to root
(i.e., will perform final delivery
rather than another network hop)
(backslashes and " marks)
can be stripped from addresses if the
If the mailer is capable of sending to more than one user
then the argv template containing
will be repeated for each unique user
flag will mark the mailer as being
configuration option must be given
for this to be effective.
This flag applies to the mailer that the message is received from,
rather than the mailer being sent to;
the domain spec of the sender
and is appended to any addresses in the message
that do not already contain a domain spec.
To: wnj@monet, mckusick@ucbarpa
flag is defined in the mailer corresponding to
Other flags are described
The S and R fields in the mailer description
are per-mailer rewriting sets
to be applied to sender and recipient addresses
These are applied after the sending domain is appended
and the general rewriting sets
but before the output rewrite
A typical use is to append the current domain
to addresses that do not already have a domain.
depending on the domain it is being shipped into.
These sets can also be used
to do special purpose output rewriting
in cooperation with ruleset four.
The E field defines the string to use
as an end-of-line indication.
A string containing only newline is the default.
The usual backslash escapes
an argv template is given as the E field.
It may have embedded spaces.
If there is no argv with a
If the pathname for this mailer is
is the optional port number
.ta \w'Mlocal, 'u +\w'P=/bin/mail, 'u +\w'F=rlsm, 'u +\w'S=10, 'u +\w'R=20, 'u
Mlocal, P=/bin/mail, F=rlsm S=10, R=20, A=mail \-d $u
Mether, P=[IPC], F=meC, S=11, R=21, A=IPC $h, M=100000
specifies a mailer to do local delivery
and a mailer for ethernet delivery.
quotes should be stripped from addresses,
and multiple users can be delivered at once;
should be applied to sender addresses in the message
should be applied to recipient addresses;
the argv to send to a message will be the word
and words containing the name of the receiving user.
it will be between the words
The second mailer is called
it should be connected to via an IPC connection,
it can handle multiple users at once,
connections should be deferred,
and any domain from the sender address
should be appended to any receiver name
sender addresses should be processed by ruleset eleven
and recipient addresses by ruleset twenty-one.
There is a 100,000 byte limit on messages passed through this mailer.
Arguments must be presented with flags before addresses.
The sender's machine address is
This flag is ignored unless the real user
contains an exclamation point
(because of certain restrictions in UUCP).
This represents the number of times this message has been processed
(to the extent that it is supported by the underlying networks).
is incremented during processing,
throws away the message with an error.
Sets the full name of this user to
Don't do aliasing or forwarding.
lines, and send to everyone listed in those lists.
line will be deleted before sending.
Any addresses in the argument vector will be deleted
a Run in arpanet mode (see below)
s Speak SMTP on input side
v Just verify addresses, don't collect or deliver
i Initialize the alias database
z Freeze the configuration file
The special processing for the
line from the header to find the sender,
(preceded by three digit reply codes for compatibility with
[Neigus73, Postel74, Postel77]),
and ending lines of error messages with <CRLF>.
Try to process the queued up mail.
a sendmail will run through the queue at the specified interval
otherwise, it only runs once.
Use a different configuration file.
runs as the invoking user (rather than root)
when this flag is specified.
These options are described in Appendix B.
There are a number of options that may be specified as
(provided for compatibility with
These are the e, i, m, and v options.
.+c "CONFIGURATION OPTIONS"
The following options may be set using the
line in the configuration file.
Many of them cannot be specified unless the invoking user is trusted.
in the current directory.
entry to exist in the alias database
Set the blank substitution character to
Unquoted spaces in addresses are replaced by this character.
If an outgoing mailer is marked as being expensive,
don't connect immediately.
This requires that queueing be compiled in,
since it will depend on a queue run process to
i Deliver interactively (synchronously)
b Deliver in background (asynchronously)
q Just queue the message (deliver during queue run)
rebuild the alias database if necessary and possible.
If this option is not set,
will never rebuild the alias database
unless explicitly requested
Dispose of errors using mode
p Print error messages (default)
q No messages, just give exit status
w Write back errors (mail if user not logged in)
e Mail back errors and give zero exit stat always
644 and 600 are good choices.
lines at the front of headers.
Normally they are assumed redundant
Ignore dots in incoming messages.
Set the default log level to
This is intended only for use from the command line.
even if I am in an alias expansion.
The name of the home network;
The the argument of an SMTP
command is checked against
is requested from the kernel for the current connection.
lines are augmented by the name that is determined in this manner
so that messages can be traced accurately.
Assume that the headers may be in old format,
if any recipient address contains a comma, parenthesis,
it will be assumed that commas already exist.
only commas delimit names.
Headers are always output with commas between the names.
Log statistics in the named
Be super-safe when running things,
always instantiate the queue file,
even if you are going to attempt immediate delivery.
always instantiates the queue file
before returning control the the client
messages that have not been successfully sent
will be returned to the sender.
Set the local timezone name to
this is only used under version six.
Set the default userid for mailers to
flag in the mailer definition
When the system load average exceeds
(i.e., don't try to send them).
When the system load average exceeds
refuse incoming SMTP connections.
The following flags may be set in the mailer description.
but only if this is a network forward operation
the mailer will give an error
does not have special permissions).
before calling the mailer.
This would be used in a secure environment
This could be used to avoid forged addresses.
This flag is suppressed if given from an
(e.g, a user's mail.cf file).
Do not insert a UNIX-style
line on the front of the message.
final delivery will be performed).
Strip quote characters off of the address
before calling the mailer.
This mailer can send to multiple users
part of the mailer definition,
that field will be repeated as necessary
for all qualifying users.
Upper case should be preserved in user names
Upper case should be preserved in host names
This is an Arpanet-compatible mailer,
and all appropriate modes should be set.
This mailer wants Unix-style
lines with the ugly UUCP-style
This mailer is expensive to connect to,
so try to avoid connecting normally;
any necessary connection will occur during a queue run.
This mailer want to use the hidden dot algorithm
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.
Limit the line lengths as specified in RFC821.
Use the return-path in the SMTP
rather than just the return address;
although this is required in RFC821,
many hosts do not process return paths properly.
This mailer will be speaking SMTP
as such it can use special protocol features.
This option is not required
if this option is omitted the transmission will still operate successfully,
although perhaps not as efficiently as possible).
from a mailer with this flag set,
any addresses in the header that do not have an at sign
after being rewritten by ruleset three
This allows mail with headers of the form:
To: userb@hostb, userc@hosta
Escape lines beginning with
in the message with a `>' sign.
.+c "OTHER CONFIGURATION"
There are some configuration changes that can be made by
These are located in three places:
These contain operating-system dependent descriptions.
They are interpolated into the Makefiles in the
This includes information about what version of UNIX
what libraries you have to include, etc.
Configuration parameters that may be tweaked by the installer
Some special routines and a few variables
may be defined in conf.c.
For the most part these are selected from the settings
.uh "Parameters in md/config.m4"
The following compilation flags may be defined in the
to define the environment in which you are operating.
this will compile a version 6 system,
single character tty id's,
you will be assumed to have a Berkeley 4BSD or 4.1BSD,
special types defined in <sys/types.h>
If none of these flags are set,
a version 7 system is assumed.
You will also have to specify what libraries to link with
Most notably, you will have to include
if you are running a 4.1BSD system.
.uh "Parameters in src/conf.h"
Parameters and compilation options
Most of these need not normally be tweaked;
common parameters are all in sendmail.cf.
However, the sizes of certain primitive vectors, etc.,
are included in this file.
The numbers following the parameters
The maximum line length of any input line.
If message lines exceed this length
they will still be processed correctly;
configuration file lines,
must fit within this limit.
The maximum length of any name,
such as a host or a user name.
The maximum total length of any header field,
including continuation lines.
The maximum number of parameters to any mailer.
This limits the number of recipients that may be passed in one transaction.
When a message has been processed more than this number of times,
sendmail rejects the message
on the assumption that there has been an aliasing loop.
This can be determined from the
or by counting the number of trace fields
The maximum number of atoms
The maximum number of mailers that may be defined
in the configuration file.
The maximum number of rewriting sets
The maximum number of values for the
field that may be defined
The maximum number of trusted users that may be defined
A number of other compilation options exist.
These specify whether or not specific code should be compiled in.
(see DBM(3X) in [UNIX80]).
a much less efficient algorithm for processing aliases is used.
If set, debugging information is compiled in.
To actually get the debugging output,
routine in use at some sites is used.
This makes an informational log record
for each message processed,
and makes a higher priority log record
for internal system errors.
This flag should be set to compile in the queueing code.
mailers must accept the mail immediately
or it will be returned to the sender.
the code to handle user and server SMTP will be compiled in.
This is only necessary if your machine has some mailer
code to run a daemon is compiled in.
that there are bugs in the 4.1a code
that make it impossible for
If you have a UUCP host adjacent to you which is not running
you will have to set this flag to include the
Otherwise, UUCP gets confused about where the mail came from.
If you are using a non-UNIX mail format,
you can set this flag to turn off special processing
.uh "Configuration in src/conf.c"
Not all header semantics are defined in the configuration file.
Header lines that should only be included by certain mailers
(as well as other more obscure semantics)
This table contains the header name
(which should be in all lower case)
and a set of header control flags (described below),
Normally when the check is made to see if a header line is compatible
will not delete an existing line.
even existing header lines.
if this bit is set and the mailer does not have flag bits set
that intersect with the required mailer flags
in the header definition in
If this header field is set,
treat it like a blank line,
it will signal the end of the header
and the beginning of the message text.
even if one existed in the message before.
If a header entry does not have this bit set,
will not add another header line if a header line
of this name already existed.
This would normally be used to stamp the message
by everyone who handled it.
If the number of trace fields in a message
on the assumption that it has an aliasing loop.
this field contains recipient addresses.
flag to determine who to send to
when it is collecting recipients from the message.
This flag indicates that this field
The order of these fields in the
for which field to return error messages to.
.ta 4n +\w'"return-receipt-to", 'u
struct hdrinfo HdrInfo[] =
/* originator fields, most to least significant */
/* message identification and control */
"received", H_TRACE|H_FORCE,
This structure indicates that the
all specify recipient addresses.
field will be deleted unless the required mailer flag
(indicated in the configuration file)
fields will terminate the header;
these are specified in new protocols
or used by random dissenters around the network world.
field will always be added,
and can be used to trace messages.
There are a number of important points here.
header fields are not added automatically just because they are in the
they must be specified in the configuration file
in order to be added to the message.
Any header fields mentioned in the configuration file but not
structure have default processing performed;
they are added unless they were in the message already.
structure only specifies cliched processing;
certain headers are processed specially by ad hoc code
regardless of the status specified in
fields are always scanned on ARPANET mail
this is used to perform the
fields are used to determine the full name of the sender
this is stored in the macro
and used in a number of ways.
also contains the specification of ARPANET reply codes.
There are four classifications these fall into:
.ta \w'char 'u +\w'Arpa_TUsrerr[] = 'u +\w'"888"; 'u
char Arpa_Info[] = "050"; /* arbitrary info */
char Arpa_TSyserr[] = "455"; /* some (transient) system error */
char Arpa_PSyserr[] = "554"; /* some (transient) system error */
char Arpa_Usrerr[] = "554"; /* some (fatal) user error */
is for any information that is not required by the protocol,
such as forwarding information.
is printed out for transient errors,
is printed for permanent errors;
the distinction is made based on the value of
is the result of a user error
these are generated when the user has specified something wrong,
and hence the error is permanent,
it will not work simply by resubmitting the request.
If it is necessary to restrict mail through a relay,
This routine is called for every recipient address.
to indicate that the address is acceptable
and mail processing will continue,
to print an error message
saying why the message is rejected.
.ta 4n +4n +4n +4n +4n +4n +4n
if (MsgSize > 50000 && to->q_mailer != LocalMailer)
usrerr("Message too large for non-local delivery");
This would reject messages greater than 50000 bytes
flag can be sent to supress the return of the actual body
of the message in the error return.
The actual use of this routine is highly dependent on the
and use should be limited.
.+c "SUMMARY OF SUPPORT FILES"
This is a summary of the support files
A link to /usr/lib/sendmail;
causes the alias database to be rebuilt.
Running this program is completely equivalent to giving
Prints a listing of the mail queue.
This program is equivalent to using the
represented as a memory image.
A statistics file; need not be present.
The textual version of the alias file.
.ip /usr/lib/aliases.{pag,dir}
The program to do logging.
The configuration file for syslog.
Contains the process id of the currently running syslog.
The directory in which the mail queue
and temporary files reside.
.ip /usr/spool/mqueue/qf*
Control (queue) files for messages.
.ip /usr/spool/mqueue/df*
.ip /usr/spool/mqueue/lf*
.ip /usr/spool/mqueue/tf*
Temporary versions of the qf files,
used during queue file rebuild.
.ip /usr/spool/mqueue/nf*
A file used when creating a unique id.
.ip /usr/spool/mqueue/xf*
A transcript of the current session.
INSTALLATION AND OPERATION GUIDE
.\" remove some things to avoid "out of temp file space" problem