xref: /original-bsd/usr.sbin/sendmail/doc/op/op.me (revision b64b0d54)

.if n .ls 2
.he 'Sendmail Installation and Operation Guide''%'
.fo 'Version 3.18'DRAFT'Last Mod 02/26/83'
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.+c
.(l C
.sz 16
.b SENDMAIL
.sz 12
.sp
.b "INSTALLATION AND OPERATION GUIDE"
.sz 10
.sp
.r
Eric Allman
Britton-Lee, Inc.
.sp
Version 3.18
.)l
.sp
.(l F
.b NOTE:
.i
This is a working paper, not a specification.
Details of operation of
.r sendmail
may change as necessary
before final release.
.)l
.sp 2
.pp
.i Sendmail
implements a general purpose internetwork mail routing facility
under the UNIX*
.(f
*UNIX is a trademark of Bell Laboratories.
.)f
operating 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 configuration file.
.pp
Due to the requirements of flexibility
for
.i sendmail ,
the configuration file can seem somewhat unapproachable.
However, there are only a few basic configurations
for most sites,
for which standard configuration files have been supplied.
Most other configurations
can be built by adjusting an existing configuration files
incrementally.
.pp
Although
.i 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.
.pp
Section one describes how to do a basic
.i 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 sufficient information
for you to install
.i sendmail
and keep it happy.
Section three
describes some parameters that may be safely tweaked.
Section four
has information regarding the command line arguments.
Section five
contains the nitty-gritty information about the configuration
file.
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.
.pp
The references in this paper are actually found
in the companion paper
.ul
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"
.pp
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 parse addresses,
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.
.pp
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
.i sendmail
subtree.
.sh 2 "Off-The-Shelf Configurations"
.pp
The configuration files
are all in the subdirectory
.i cf
of the sendmail directory.
The ones used at Berkeley are in
.i m4 \|(1)
format;
files with names ending
.q .m4
are
.i m4
include files,
while files with names ending
.q .mc
are the master files.
Files with names ending
.q .cf
are the
.i m4
processed versions of the corresponding
.q .mc
file.
.pp
Two off the shelf configuration files are supplied
to handle the basic cases:
.i cf/arpaproto.cf
for Arpanet (TCP) sites
and
.i cf/uucpproto.cf
for UUCP sites.
These are
.i not
in
.i m4
format.
There are two parameters you will have to adjust
in each of these files.
The line beginning
.q DH
defines the canonical name of your host.
The line beginning
.q CH
defines the names that your host might be known by;
it should include the name listed in the
.q DH
line
and any aliases that your host goes by.
For example, a configuration might include the lines:
.(b
DHucsfcgl
CHucsfcgl cgl
.)b
This would indicate that the
.q standard
name for the host is
.q ucsfcgl
and that it is known by the names
.q ucsfcgl
and
.q cgl.
.pp
The changed file should be renamed;
in the above example,
the file might be renamed
.i ucsfcgl.cf.
This file
is now ready for installation as
.i /usr/lib/sendmail.cf .
.sh 2 "Installation Using the Makefile"
.pp
A makefile exists in the root of the
.i sendmail
directory that will do all of these steps
for a 4.2bsd system.
It may have to be slightly tailored
for use on other systems.
.pp
Before using this makefile,
you should already have created your configuration file
and left it in the file
.q cf/\fIsystem\fP.cf
where
.i system
is the name of your system
(i.e., what is returned by
.i hostname \|(1)).
If you do not have
.i hostname
you can use the declaration
.q HOST=\fIsystem\fP
on the
.i make \|(1)
command line.
.pp
The basic installation procedure is to type:
.(b
make
make install
.)b
in the root directory of the
.i sendmail
distribution.
This will make all binaries
and install them in the standard places.
The second
.i make
command must be executed as the superuser (root).
.sh 2 "Installation by Hand"
.pp
Along with building a configuration file,
you will have to install the
.i sendmail
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).
.sh 3 "lib/libsys.a"
.pp
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 required).
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:
.(b
cd lib
make ndir
.)b
This will compile and install the 4.2 compatibility routines
in the library.
You should then type:
.(b
cd lib      # if required
make
.)b
This will recompile and fill the library.
.sh 3 "/usr/lib/sendmail"
.pp
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:
.(b
cd src
rm \-f *.o
make
cp sendmail /usr/lib
.)b
.sh 3 "/usr/lib/sendmail.cf"
.pp
The configuration file
that you created earlier
should be installed in /usr/lib/sendmail.cf:
.(b
cp cf/\fIsystem\fP.cf /usr/lib/sendmail.cf
.)b
.sh 3 "/usr/ucb/newaliases"
.pp
If you are running delivermail,
it is critical that the
.i newaliases
command be replaced.
This can just be a link to
.i sendmail :
.(b
rm \-f /usr/ucb/newaliases
ln /usr/lib/sendmail /usr/ucb/newaliases
.)b
.sh 3 "/usr/lib/sendmail.cf"
.pp
The configuration file must be installed in /usr/lib.
This is described above.
.sh 3 "/usr/spool/mqueue"
.pp
The directory
.i /usr/spool/mqueue
should be created to hold the mail queue.
This directory should be mode 777
unless
.i sendmail
is run setuid,
when
.i mqueue
should be owned by the sendmail owner
and mode 755.
.sh 3 "/usr/lib/aliases*"
.pp
The system aliases are held in three files.
The file
.q /usr/lib/aliases
is the master copy.
A sample is given in
.q lib/aliases
which includes some aliases which
.i must
be defined:
.(b
cp lib/aliases /usr/lib/aliases
.)b
You should extend this file with any aliases that are apropos to your system.
.pp
Normally
.i sendmail
looks at a version of these files maintained by the
.i dbm \|(3)
routines.
These are stored in
.q /usr/lib/aliases.dir
and
.q /usr/lib/aliases.pag.
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:
.(b
cp /dev/null /usr/lib/aliases.dir
cp /dev/null /usr/lib/aliases.pag
chmod 666 /usr/lib/aliases.*
newaliases
.)b
.sh 3 "/usr/lib/sendmail.fc"
.pp
If you intend to install the frozen version of the configuration file
(for quick startup)
you should create the file /usr/lib/sendmail.fc
and initialize it.
This step may be safely skipped.
.(b
cp /dev/null /usr/lib/sendmail.fc
/usr/lib/sendmail \-bz
.)b
.sh 3 "/etc/rc"
.pp
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.
.pp
Add the following lines to
.q /etc/rc
(or
.q /etc/rc.local
as appropriate)
in the area where it is starting up the daemons:
.(b
if [ \-f /usr/lib/sendmail ]; then
	(cd /usr/spool/mqueue; rm \-f lf*)
	/usr/lib/sendmail \-bd \-q10m &
	echo \-n ' sendmail' >/dev/console
fi
.)b
The
.q cd
and
.q rm
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
.i sendmail
has two flags:
.q \-bd
causes it to listen on the SMTP port,
and
.q \-q10m
causes it to run the queue every ten minutes.
.pp
If you are not running a version of UNIX
that supports Berkeley TCP/IP,
do not include the
.b \-bd
flag.
.sh 3 "/usr/lib/sendmail.hf"
.pp
This is the help file used by the SMTP
.b HELP
command.
It should be copied from
.q lib/sendmail.hf :
.(b
cp lib/sendmail.hf /usr/lib
.)b
.sh 3 "/usr/lib/sendmail.st"
.pp
If you wish to collect statistics
about your mail traffic,
you should create the file
.q /usr/lib/sendmail.st :
.(b
cp /dev/null /usr/lib/sendmail.st
chmod 666 /usr/lib/sendmail.st
.)b
This file does not grow.
It is printed with the program
.q aux/mailstats.
.sh 3 "/etc/syslog"
.pp
You may want to run the
.i syslog
program
(to collect log information about sendmail).
This program normally resides in
.i /etc/syslog,
with support files
.i /etc/syslog.conf
and
.i /etc/syslog.pid .
The program is located in the
.i aux
subdirectory of the
.i sendmail
distribution.
The file
.i /etc/syslog.conf
describes the file(s) that sendmail will log in.
For a complete description of syslog,
see the manual page for
.i syslog \|(8)
(located in
.i sendmail/doc
on the distribution).
.sh 3 "/usr/ucb/newaliases"
.pp
If
.i sendmail
is invoked as
.q newaliases,
it will simulate the
.b \-bi
flag
(i.e., will rebuild the alias database;
see below).
This should be a link to /usr/lib/sendmail.
.sh 3 "/usr/ucb/mailq"
.pp
If
.i sendmail
is invoked as
.q mailq,
it will simulate the
.b \-bp
flag
(i.e.,
.i sendmail
will print the contents of the mail queue;
see below).
This should be a link to /usr/lib/sendmail.
.sh 1 "NORMAL OPERATIONS"
.sh 2 "Quick Configuration Startup"
.pp
A fast version of the configuration file
may be set up by using the
.b \-bz
flag:
.(b
/usr/lib/sendmail \-bz
.)b
This creates the file
.i /usr/lib/sendmail.fc
(\c
.q "frozen configuration" ).
This file is an image of
.i sendmail 's
data space after reading in the configuration file.
If this file exists,
it is used instead of
.i /usr/lib/sendmail.cf
.i sendmail.fc
must be rebuilt manually every time
.i sendmail.cf
is changed.
.pp
The frozen configuration file will be ignored
if a
.b \-C
flag is specified
or if sendmail detects that it is out of date.
However, the heuristics are not strong
so this should not be trusted.
.sh 2 "The System Log"
.pp
The system log is supported by the
.i syslog \|(8)
program.
.sh 3 "Format"
.pp
Each line in the system log
consists of a timestamp,
the name of the machine that generated it
(for logging from several machines
over the ethernet),
the word
.q sendmail: ,
and a message.
.sh 3 "Levels"
.pp
If you have
.i syslog \|(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
.q useful;
log levels above ten
are usually for debugging purposes.
.pp
A complete description of the log levels
is given in section 4.3.
.sh 2 "The Mail Queue"
.pp
The mail queue should be processed transparently.
However, you may find 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 gracefully when the host comes up,
you may find performance unacceptably bad in the meantime.
.sh 3 "Printing the queue"
.pp
The contents of the queue can be printed
using the
.i mailq
command
(or by specifying the
.b \-bp
flag to sendmail):
.(b
mailq
.)b
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.
.sh 3 "Format of queue files"
.pp
All queue files have the form
\fIx\fP\|\fBf\fP\fIAA99999\fP
where
.i AA99999
is the
.i id
for this file
and the
.i x
is a type.
The types are:
.ip d
The data file.
The message body (excluding the header) is kept in this file.
.ip l
The lock file.
If this file exists,
the job is currently being processed,
and a queue run will not process the file.
For that reason,
an extraneous
.b lf
file can cause a job to apparently disappear
(it will not even time out!).
.ip n
This file is created when an id is being created.
It is a separate file to insure that no mail can ever be destroyed
due to a race condition.
It should exist for no more than a few milliseconds
at any given time.
.ip q
The queue control file.
This file contains the information necessary to process the job.
.ip t
A temporary file.
These are an image of the
.b qf
file when it is being rebuilt.
It should be renamed to a
.b qf
file very quickly.
.ip x
A transcript file,
existing during the life of a session
showing everything that happens
during that session.
.pp
The
.b qf
file is structured as a series of lines
each beginning with a code letter.
The lines are as follows:
.ip D
The name of the data file.
There may only be one of these lines.
.ip H
A header definition.
There may be any number of these lines.
The order is important:
they represent the order in the final message.
These use the same syntax
as header definitions in the configuration file.
.ip 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.
.ip S
The sender address.
There may only be one of these lines.
.ip T
The job creation time.
This is used to compute when to time out the job.
.ip P
The current message priority.
This is used to order the queue.
Higher numbers mean lower priorities.
The priority drops
as the message sits in the queue.
The initial priority depends on the message class
and the size of the message.
.ip M
A message.
This line is printed by the
.i mailq
command,
and is generally used to store status information.
It can contain any text.
.pp
As an example,
the following is a queue file sent to
.q mckusick@calder
and
.q wnj :
.(b
DdfA13557
Seric
T404261372
P132
Rmckusick@calder
Rwnj
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)
Hphone: (415) 548-3211
HTo: mckusick@calder, wnj
.)b
This shows the name of the data file,
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.
.sh 3 "Forcing the queue"
.pp
.i Sendmail
should run the queue automatically
at intervals.
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,
.i sendmail
first checks to see if the job is locked.
If so, it ignores the job.
.pp
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.
Due to the locking algorithm,
it is impossible for one job to freeze the queue.
However,
an uncooperative recipient host
or a program recipient
that never returns
can accumulate many processes in your system.
Unfortunately,
there is no way to resolve this
without violating the protocol.
.pp
In some cases,
you may find that a major host going down
for a couple of days
may create a prohibitively large queue.
This will result in
.i sendmail
spending an inordinate amount of time
sorting the queue.
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.
.pp
To do this,
it is acceptable to move the entire queue directory:
.(b
cd /usr/spool
mv mqueue omqueue; mkdir mqueue; chmod 777 mqueue
.)b
You should then kill the existing daemon
(since it will still be processing in the old queue directory)
and create a new daemon.
.pp
To run the old mail queue,
run the following command:
.(b
/usr/lib/sendmail \-oQ/usr/spool/omqueue \-q
.)b
The
.b \-oQ
flag specifies an alternate queue directory
and the
.b \-q
flag says to just run every job in the queue.
If you have a tendency toward voyeurism,
you can use the
.b \-v
flag to watch what is going on.
.pp
When the queue is finally emptied,
you can remove the directory:
.(b
rmdir /usr/spool/omqueue
.)b
.sh 2 "The Alias Database"
.pp
The alias database exists in two forms.
One is a text form,
maintained in the file
.i /usr/lib/aliases.
The aliases are of the form
.(b
name: name1, name2, ...
.)b
Only local names may be aliased;
e.g.,
.(b
eric@mit-xx: eric@berkeley
.)b
will not have the desired effect.
Aliases may be continued by starting any continuation lines
with a space or a tab.
Blank lines and lines beginning with a sharp sign
(\c
.q # )
are comments.
.pp
The second form is processed by the
.i dbm \|(3)
library.
This form is in the files
.i /usr/lib/aliases.dir
and
.i /usr/lib/aliases.pag.
This is the form that
.i sendmail
actually uses to resolve aliases.
This technique is used to improve performance.
.sh 3 "Rebuilding the alias database"
.pp
The DBM version of the database
may be rebuilt explicitly by executing the command
.(b
newaliases
.)b
This is equivalent to giving
.i sendmail
the
.b \-bi
flag:
.(b
/usr/lib/sendmail \-bi
.)b
.pp
If the
.q D
option is specified in the configuration,
.i sendmail
will rebuild the alias database automatically
if possible
when it is out of date.
The conditions under which it will do this are:
.np
The DBM version of the database is mode 666.   -or-
.np
.i Sendmail
is running setuid to root.
.lp
Auto-rebuild can be dangerous
on heavily loaded machines
with large alias files;
if it might take more than five minutes
to rebuild the database,
there is a chance that several processes will start the rebuild process
simultaneously.
.sh 3 "Potential problems"
.pp
There are a number of problems that can occur
with the alias database.
They all result from a
.i 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.
.pp
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.
Second,
at the end of the rebuild
it adds an alias of the form
.(b
@: @
.)b
(which is not normally legal).
Before sendmail will access the database,
it checks to insure that this entry exists\**.
.(f
\**The
.q a
option is required in the configuration
for this action to occur.
This should normally be specified
unless you are running
.i delivermail
in parallel with
.i sendmail.
.)f
It will wait up to five minutes
for this entry to appear,
at which point it will force a rebuild itself\**.
.(f
\**Note:
the
.q D
option must be specified in the configuration file
for this operation to occur.
.)f
.sh 3 "List owners"
.pp
If an error occurs on sending to a certain address,
say
.q \fIx\fP ,
.i sendmail
will look for an alias
of the form
.q owner-\fIx\fP
to receive the errors.
This is typically useful
for a mailing list
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.
For example:
.(b
unix-wizards: eric@ucbarpa, wnj@monet, nosuchuser,
	sam@matisse
owner-unix-wizards: eric@ucbarpa
.)b
would cause
.q eric@ucbarpa
to get the error that will occur
when someone sends to
unix-wizards
due to the inclusion of
.q nosuchuser
on the list.
.sh 2 "Per-User Forwarding (.forward Files)"
.pp
As an alternative to the alias database,
any user may put a file with the name
.q .forward
in his or her home directory.
If this file exists,
.i sendmail
redirects mail for that user
to the list of addresses listed in the .forward file.
For example, if the home directory for user
.q mckusick
has a .forward file with contents:
.(b
mckusick@ernie
kirk@calder
.)b
then any mail arriving for
.q mckusick
will be redirected to the specified accounts.
.sh 2 "Special Header Lines"
.pp
Several header lines have special interpretations
defined by the configuration file.
Others have interpretations built into
.i sendmail
that cannot be changed without changing the code.
These builtins are described here.
.sh 3 "Return-receipt-to"
.pp
If this header is sent,
a message will be sent to any specified addresses
when the final delivery is complete.
This is determined by the
.b l
flag in the mailer descriptor.
.sh 3 "Errors-to"
.pp
If errors occur anywhere during processing,
this header will cause error messages to go to
the listed addresses
rather than to the sender.
This is intended for mailing lists.
.sh 3 "Apparently-To:
.pp
If a message comes in with no recipients listed in the message
(in a To:, Cc:, or Bcc: line)
then
.i sendmail
will add an
.q "Apparently-To:"
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.
.pp
At least one recipient line is required under RFC 822.
.sh 1 "ARGUMENTS"
.pp
The complete list of arguments to
.i sendmail
is described in detail in Appendix A.
Some important arguments are described here.
.sh 2 "Queue Interval"
.pp
The amount of time between forking a process
to run through the queue
is defined by the
.b \-q
flag.
If you run in mode
.b f
or
.b a
this can be relatively large,
since it will only be relevant
when a host that was down comes back up.
If you run in
.b q
mode
it should be relatively short,
since it defines the maximum amount of time that a message
may sit in the queue.
.sh 2 "Daemon Mode"
.pp
If you allow incoming mail over an IPC connection,
you should have a daemon running.
This should be set by your
.i /etc/rc
file using the
.b \-bd
flag.
The
.b \-bd
flag and the
.b \-q
flag may be combined in one call:
.(b
/usr/lib/sendmail \-bd \-q10m
.)b
.sh 2 "Forcing the Queue"
.pp
In some cases you may find that the queue has gotten clogged for some reason.
You can force a queue run
using the
.b \-q
flag (with no value).
It is frequently entertaining to use the
.b \-v
flag (verbose)
when this is done to watch what happens:
.(b
/usr/lib/sendmail \-q \-v
.)b
.sh 2 "Debugging"
.pp
There are a fairly large number of debug flags
built into
.i sendmail .
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
.q 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.
Debug flags are set using the
.b \-d
option;
the syntax is:
.(b
.ta \w'debug-option  'u
debug-flag:	\fB\-d\fP debug-list
debug-list:	debug-option [ , debug-option ]
debug-option:	debug-range [ . debug-level ]
debug-range:	integer | integer \- integer
debug-level:	integer
.)b
where spaces are for reading ease only.
For example,
.(b
\-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
.)b
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"
.pp
An alternative configuration file
can be specified using the
.b \-C
flag; for example,
.(b
/usr/lib/sendmail \-Ctest.cf
.)b
uses the configuration file
.i test.cf
instead of the default
.i /usr/lib/sendmail.cf.
If the
.b \-C
flag has no value
it defaults to
.i sendmail.cf
in the current directory.
.sh 2 "Changing the Values of Options"
.pp
Options can be overridden using the
.b \-o
flag.
For example,
.(b
/usr/lib/sendmail \-oT2m
.)b
sets the
.b T
(timeout) option to two minutes
for this run only.
.sh 1 "TUNING"
.pp
There are a number of configuration parameters
you may want to change,
depending on the requirements of your site.
Most of these are set
using an option in the configuration file.
For example,
the line
.q OT3d
sets option
.q T
to the value
.q 3d
(three days).
.sh 2 "Timeouts"
.pp
All time intervals are set
using a scaled syntax.
For example,
.q 10m
represents ten minutes, whereas
.q 2h30m
represents two and a half hours.
The full set of scales is:
.(b
.ta 4n
s	seconds
m	minutes
h	hours
d	days
w	weeks
.)b
.sh 3 "Queue interval"
.pp
The argument to the
.b \-q
flag
specifies how often a subdaemon will run the queue.
This is typically set to between five minutes
and one half hour.
.sh 3 "Read timeouts"
.pp
It is possible to time out when reading the standard input
or when reading from a remote SMTP server.
Technically,
this is not acceptable within the published protocols.
However,
it might be appropriate to set it to something large
in certain environments
(such as an hour).
This will reduce the chance of large numbers of idle daemons
piling up on your system.
This timeout is set using the
.b r
option in the configuration file.
.sh 3 "Message timeouts"
.pp
After sitting in the queue for a few days,
a 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 typically set to three days.
This timeout is set using the
.b T
option in the configuration file.
.pp
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
for a short period
by running the queue
with a short message timeout.
For example,
.(b
/usr/lib/sendmail \-oT1d \-q
.)b
will run the queue
and flush anything that is one day old.
.sh 2 "Delivery Mode"
.pp
There are a number of delivery modes that
.i sendmail
can operate in,
set by the
.q d
configuration option.
These modes
specify how quickly mail will be delivered.
Legal modes are:
.(b
.ta 4n
i	deliver interactively (synchronously)
b	deliver in background (asynchronously)
q	queue only (don't deliver)
.)b
There are tradeoffs.
Mode
.q i
passes the maximum amount of information to the sender,
but is hardly ever necessary.
Mode
.q q
puts the minimum load on your machine,
but means that delivery may be delayed for up to the queue interval.
Mode
.q b
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.
.sh 2 "Log Level"
.pp
The level of logging can be set for sendmail.
The default using a standard configuration table is level 9.
The levels are as follows:
.ip 0
No logging.
.ip 1
Major problems only.
.ip 2
Message collections and failed deliveries.
.ip 3
Successful deliveries.
.ip 4
Messages being defered
(due to a host being down, etc.).
.ip 5
Normal message queueups.
.ip 6
Unusual but benign incidents,
e.g.,
trying to process a locked queue file.
.ip 9
Log internal queue id to external message id mappings.
This can be useful for tracing a message
as it travels between several hosts.
.ip 12
Several messages that are basically only of interest
when debugging.
.ip 16
Verbose information regarding the queue.
.sh 2 "File Modes"
.pp
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?"
.pp
.i Sendmail
can safely be made
setuid to root.
At the point where it is about to
.i exec \|(2)
a mailer,
it checks to see if the userid is zero;
if so,
it resets the userid and groupid to a default
(set by the
.b u
and
.b g
options).
(This can be overridden
by setting the
.b S
flag to the mailer
for mailers that are trusted
and must be called as root.)
However,
this will cause mail processing
to be accounted
(using
.i sa \|(8))
to root
rather than to the user sending the mail.
.sh 3 "Temporary file modes"
.pp
The mode of all temporary files that
.i sendmail
creates is determined by the
.q F
option.
Reasonable values for this option are
0600
and
0644.
If the more permissive mode is selected,
it will not be necessary to run
.i sendmail
as root at all
(even when running the queue).
.sh 3 "Should my alias database be writable?"
.pp
At Berkeley
we have the alias database
(/usr/lib/aliases*)
mode 666.
There are some dangers inherent in this approach:
any user can add him-/her-self
to any list,
or can
.q steal
any other user's mail.
However,
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
the rare nasty person.
.pp
The database that
.i sendmail
actually used
is represented by the two files
.i aliases.dir
and
.i aliases.pag
(both in /usr/lib).
The mode on these files should match the mode
on /usr/lib/aliases.
If
.i aliases
is writable
and the
DBM
files
(\c
.i aliases.dir
and
.i aliases.pag )
are not,
users will be unable to reflect their desired changes
through to the actual database.
However,
if
.i aliases
is read-only
and the DBM files are writable,
a slightly sophisticated user
can arrange to steal mail anyway.
.pp
If your DBM files are not writable by the world
or you do not have auto-rebuild enabled
(with the
.q D
option),
then you must be careful to reconstruct the alias database
each time you change the text version:
.(b
newaliases
.)b
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"
.pp
This section describes the configuration file
in detail,
including hints on how to write one of your own
if you have to.
.pp
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
.i sendmail
starts up,
rather than easy for a human to read or write.
On the
.q "future project"
list is a
configuration-file compiler.
.pp
An overview of the configuration file
is given first,
followed by details of the semantics.
.sh 2 "The Syntax"
.pp
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
are continuation lines
(although the semantics are not well defined in many places).
Blank lines and lines beginning with a sharp symbol
(`#')
are comments.
.sh 3 "R and S \*- rewriting rules"
.pp
The core of address parsing
are the rewriting rules.
These are an ordered production system.
.i 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.
.pp
There are several sets of rewriting rules.
Some of the rewriting sets are used internally
and must have specific semantics.
Other rewriting sets
do not have specifically assigned semantics,
and may be referenced by the mailer definitions
or by other rewriting sets.
.pp
The syntax of these two commands are:
.(b F
.b S \c
.i n
.)b
Sets the current ruleset being collected to
.i n .
If you begin a ruleset more than once
it deletes the old definition.
.(b F
.b R \c
.i lhs
.i rhs
.i comments
.)b
The
fields must be separated
by at least one tab character;
there may be embedded spaces
in the fields.
The
.i lhs
is a pattern that is applied to the input.
If it matches,
the input is rewritten to the
.i rhs .
The
.i comments
are ignored.
.sh 3 "D \*- define macro"
.pp
Macros are named with a single character.
These may be selected from the entire ASCII set,
but user-defined macros
should be selected from the set of upper case letters only.
Lower case letters
and special symbols
are used internally.
.pp
The syntax for macro definitions is:
.(b F
.b D \c
.i x\|val
.)b
where
.i x
is the name of the macro
and
.i val
is the value it should have.
Macros can be interpolated in most places using the escape sequence
.b $ \c
.i x .
.sh 3 "C and F \*- define classes"
.pp
Classes of words may be defined
to match on the left hand side of rewriting rules.
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 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.
.pp
The syntax is:
.(b F
.b C \c
.i c\|word1
.i word2...
.br
.b F \c
.i c\|file
[
.i format
]
.)b
The first form defines the class
.i c
to match any of the named words.
It is permissible to split them among multiple lines;
for example, the two forms:
.(b
CHmonet ucbmonet
.)b
and
.(b
CHmonet
CHucbmonet
.)b
are equivalent.
The second form
reads the elements of the class
.i c
from the named
.i file ;
the
.i format
is a
.i scanf \|(3)
pattern
that should produce a single string.
.sh 3 "M \*- define mailer"
.pp
Programs and interfaces to mailers
are defined in this line.
The format is:
.(b F
.b M \c
.i name ,
{\c
.i field =\c
.i value \|}*
.)b
where
.i name
is the name of the mailer
(used internally only)
and the
.q field=name
pairs define attributes of the mailer.
Fields are:
.(b
.ta 1i
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
.)b
Only the first character of the field name is checked.
.sh 3 "H \*- define header"
.pp
The format of the header lines that sendmail inserts into the message
are defined by the
.b H
line.
The syntax of this line is:
.(b F
.b H [\c
.b ? \c
.i mflags \c
.b ? ]\c
.i hname \c
.b :
.i htemplate
.)b
Continuation lines in this spec
are reflected directly into the outgoing message.
The
.i htemplate
is macro expanded before insertion into the message.
If the
.i mflags
(surrounded by question marks)
are specified,
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.
.pp
Some headers have special semantics
that will be described below.
.sh 3 "O \*- set option"
.pp
There are a number of
.q random
options that
can be set from a configuration file.
Options are represented by single characters.
The syntax of this line is:
.(b F
.b O \c
.i o\|value
.)b
This sets option
.i o
to be
.i value .
Depending on the option,
.i value
may be a string, an integer,
a boolean
(with legal values
.q t ,
.q T ,
.q f ,
or
.q F ;
the default is TRUE),
or
a time interval.
.sh 3 "T \*- define trusted users"
.pp
Trusted users
are those users who are permitted
to override the sender address
using the
.b \-f
flag.
These typically are
.q root,
.q uucp,
and
.q network,
but on some users it may be convenient
to extend this list to include other users,
perhaps to support
a separate
UUCP
login for each host.
The syntax of this line is:
.(b F
.b T \c
.i user1
.i user2 ...
.)b
There may be more than one of these lines.
.sh 3 "P \*- precedence definitions"
.pp
Values for the
.q "Precedence:"
field may be defined using the
.b P
control line.
The syntax of this field is:
.(b
\fBP\fP\fIname\fP\fB=\fP\fInum\fP
.)b
When the
.i name
is found in a
.q Precedence:
field,
the message class is set to
.i num .
Higher numbers mean higher precedence.
Numbers less than zero
have the special property
that error messages will not be returned.
The default precedence is zero.
For example,
our list of precedences is:
.(b
Pfirst-class=0
Pspecial-delivery=100
Pjunk=\-100
.)b
.sh 2 "The Semantics"
.pp
This section describes the semantics of the configuration file.
.sh 3 "Special macros, conditionals"
.pp
Macros are interpolated
using the construct
.b $ \c
.i x ,
where
.i x
is the name of the macro to be interpolated.
In particular,
lower case letters are reserved to have
special semantics,
used to pass information in or out of sendmail,
and some special characters are reserved to
provide conditionals, etc.
.pp
The following macros
.i must
be defined to transmit information into
.i sendmail:
.(b
.ta 4n
e	The SMTP entry message
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
.)b
The
.b $e
macro is printed out when SMTP starts up.
The first word must be the
.b $j
macro.
The
.b $j
macro
should be in RFC821 format.
The
.b $l
and
.b $n
macros can be considered constants
except under terribly unusual circumstances.
The
.b $o
macro consists of a list of characters
which will be considered tokens
and which will separate tokens
when doing parsing.
For example, if
.q r
were in the
.b $o
macro, then the input
.q address
would be scanned as three tokens:
.q add,
.q r,
and
.q ess.
Finally, the
.b $q
macro specifies how an address should appear in a message
when it is defaulted.
For example, on our system these definitions are:
.(b
De$j Sendmail $v ready at $b
DnMAILER-DAEMON
DlFrom $g  $d
Do.:%@!^=/
Dq$g$?x ($x)$.
Dj$H.$D
.)b
An acceptable alternative for the
.b $q
macro is
.q "$?x$x $.<$g>" .
These correspond to the following two formats:
.(b
eric@Berkeley (Eric Allman)
Eric Allman <eric@Berkeley>
.)b
.pp
Some macros are defined by
.i sendmail
for interpolation into argv's for mailers
or for other contexts.
These macros are:
.(b
a	The origination date in Arpanet format
b	The current date in Arpanet format
c	The hop count
d	The date in UNIX (ctime) format
f	The sender (from) address
g	The sender address relative to the recipient
h	The recipient host
i	The queue id
p	Sendmail's pid
r	Protocol used
s	Sender's host name
t	A numeric representation of the current time
u	The recipient user
v	The version number of sendmail
w	The hostname of this site
x	The full name of the sender
y	The id of the sender's tty
z	The home directory of the recipient
.)b
.pp
There are three types of dates that can be used.
The
.b $a
and
.b $b
macros are in Arpanet format;
.b $a
is the time as extracted from the
.q Date:
line of the message
(if there was one),
and
.b $b
is the current date and time
(used for postmarks).
If no
.q Date:
line is found in the incoming message,
.b $a
is set to the current time also.
The
.b $d
macro is equivalent to the
.b $a
macro in UNIX
(ctime)
format.
.pp
The
.b $f
macro is the id of the sender
as originally determined;
when mailing to a specific host
the
.b $g
macro is set to the address of the sender
.ul
relative to the recipient.
For example,
if I send to
.q bollard@matisse
from the machine
.q ucbarpa
the
.b $f
macro will be
.q eric
and the
.b $g
macro will be
.q eric@ucbarpa.
.pp
The
.b $x
macro is set to the full name of the sender.
This can be determined in several ways.
It can be passed as flag to
.i sendmail.
The second choice is the value of the
.q Full-name:
line in the header if it exists,
and the third choice is the comment field
of a
.q From:
line.
If all of these fail,
and if the message is being originated locally,
the full name is looked up in the
.i /etc/passwd
file.
.pp
When sending,
the
.b $h ,
.b $u ,
and
.b $z
macros get set to the host, user, and home directory
(if local)
of the recipient.
The first two are set from the
.b $@
and
.b $:
part of the rewriting rules, respectively.
.pp
The
.b $p
and
.b $t
macros are used to create unique strings
(e.g., for the
.q Message-Id:
field).
The
.b $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
.b $y
macro is set to the id of the terminal of the sender
(if known);
some systems like to put this
in the Unix
.q From
line.
The
.b $v
macro is set to be the version number of
.i sendmail ;
this is normally put in timestamps
and has been proven extremely useful for debugging.
The
.b $w
macro is set to the name of this host
if it can be determined.
The
.b $c
field is set to the
.q "hop count,"
i.e., the number of times this message has been processed.
This can be determined
by the
.b \-h
flag on the command line
or by counting the timestamps in the message.
.pp
The
.b $r
and
.b $s
fields are set to the protocol used to communicate with sendmail
and the sending hostname;
these are not supported in the current version.
.pp
Conditionals can be specified using the syntax:
.(b
$?x text1 $| text2 $.
.)b
This interpolates
.i text1
if the macro
.b $x
is set,
and
.i text2
otherwise.
The
.q else
(\c
.b $| )
clause may be omitted.
.sh 3 "Special classes"
.pp
The class
.b $=w
is set to be the set of all names
this host is known by.
This can be used to delete local hostnames.
.sh 3 "The left hand side"
.pp
The left hand side of rewriting rules contains a pattern.
Normal words are simply matched directly.
Metasyntax is introduced using a dollar sign.
The metasymbols are:
.(b
.ta \w'\fB$=\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
.)b
If any of these match,
they are assigned to the symbol
.b $ \c
.i n
for replacement on the right hand side,
where
.i n
is the index in the LHS.
For example,
if the LHS:
.(b
$\-:$+
.)b
is applied to the input:
.(b
UCBARPA:eric
.)b
the rule will match, and the values passed to the RHS will be:
.(b
.ta 4n
$1	UCBARPA
$2	eric
.)b
.sh 3 "The right hand side"
.pp
When the right hand side of a rewriting rule matches,
the input is deleted and replaced by the right hand side.
Tokens are copied directly from the RHS
unless they are begin with a dollar sign.
Metasymbols are:
.(b
.ta \w'$#mailer  'u
\fB$\fP\fIn\fP	Substitute indefinite token \fIn\fP from LHS
\fB$>\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
.)b
.pp
The
.b $ \c
.i n
syntax substitutes the corresponding value from a
.b $+ ,
.b $\- ,
.b $* ,
.b $= ,
or
.b $~
match on the LHS.
It may be used anywhere.
.pp
The
.b $> \c
.i n
syntax
causes the remainder of the line to be substituted as usual
and then passed as the argument to ruleset
.i n .
The final value of ruleset
.i n
then becomes
the substitution for this rule.
.pp
The
.b $#
syntax should
.i only
be used in ruleset zero.
It causes evaluation of the ruleset to terminate immediately,
and signals to sendmail that the address has completely resolved.
The complete syntax is:
.(b
\fB$#\fP\fImailer\fP\fB$@\fP\fIhost\fP\fB$:\fP\fIuser\fP
.)b
This specifies the
{mailer, host, user}
3-tuple necessary to direct the mailer.
If the mailer is local
the host part may be omitted.
The
.i mailer
and
.i host
must be a single word,
but the
.i user
may be multi-part.
.pp
A RHS may also be preceeded by a
.b $@
or a
.b $:
to control evaluation.
A
.b $@
prefix causes the ruleset to return with the remainder of the RHS
as the value.
A
.b $:
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.
.pp
The
.b $@
and
.b $:
prefixes may preceed a
.b $>
spec;
for example:
.(b
.ta 8n
R$+	$:$>7$1
.)b
matches anything,
passes that to ruleset seven,
and continues;
the
.b $:
is necessary to avoid an infinite loop.
.sh 3 "Semantics of rewriting rule sets"
.pp
There are five rewriting sets
that have specific semantics.
These are related as depicted by figure 2.
.(z
.hl
.ie t .sp 2i
.el \{\
.(c
                    +---+
                 -->| 0 |-->resolved address
                /   +---+
               /            +---+   +---+
              /        ---->| 1 |-->| S |--
       +---+ / +---+  /     +---+   +---+  \e    +---+
addr-->| 3 |-->| D |--                      --->| 4 |-->msg
       +---+   +---+  \e     +---+   +---+  /    +---+
                        --->| 2 |-->| R |--
                            +---+   +---+
.)c

.ce
Figure 2 \*- Rewriting set semantics
.(c
D \*- sender domain addition
S \*- mailer-specific sender rewriting
R \*- mailer-specific recipient rewriting
.)c
.\}
.hl
.)z
.pp
Ruleset three
should turn the address into
.q "canonical form."
This form should have the basic syntax:
.(b
local-part@host-domain-spec
.)b
If no
.q @
sign is specified,
then the
host-domain-spec
.i may
be appended from the
sender address
(if the
.b C
flag is set in the mailer definition
corresponding to the
.i sending
mailer).
Ruleset three
is applied by sendmail
before doing anything with any address.
.pp
Ruleset zero
is applied after ruleset three
to addresses that are going to actually specify recipients.
It must resolve to a
.i "{mailer, host, user}"
triple.
The
.i mailer
must be defined in the mailer definitions
from the configuration file.
The
.i host
is defined into the
.b $h
macro
for use in the argv expansion of the specified mailer.
.pp
Rulesets one and two
are applied to all sender and recipient addresses respectively.
They are applied before any specification
in the mailer definition.
They must never resolve.
.pp
Ruleset four is applied to all addresses
in the message.
It is typically used
to translate internal to external form.
.sh 3 "Mailer flags etc."
.pp
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"
.pp
The mailer with the special name
.q error
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.
For example, the entry:
.(b
$#error$:Host unknown in this domain
.)b
on the RHS of a rule
will cause the specified error to be generated
if the LHS matches.
This mailer is only functional in ruleset zero.
.sh 2 "Building a Configuration File From Scratch"
.pp
Building a configuration table from scratch is an extremely difficult job.
Fortunately,
it is almost never necessary to do so;
nearly every situation that may come up
may be resolved by changing an existing table.
In any case,
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"
.pp
The configuration table has three major purposes.
The first and simplest
is to set up the environment for
.i sendmail .
This involves setting the options,
defining a few critical macros,
etc.
Since these are described in other places,
we will not go into more detail here.
.pp
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
into a canonical form.
This should be done in ruleset three.
The second phase maps this canonical form
into the syntax appropriate for the receiving mailer.
.i Sendmail
does this in three subphases.
Rulesets one and two
are applied to all sender and recipient addresses respectively.
After this,
you may specify per-mailer rulesets
for both sender and recipient addresses;
this allows mailer-specific customization.
Finally,
ruleset four is applied to do any default conversion
to external form.
.pp
The third purpose
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
of the mailer.
.sh 3 "Philosophy"
.pp
The particular philosophy you choose will depend heavily
on the size and structure of your organization.
I will present a few possible philosophies here.
.pp
One general point applies to all of these philosophies:
it is almost always a mistake
to try to do full name resolution.
For example,
if you are trying to get names of the form
.q user@host
to the Arpanet,
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
is to simply forward to
.q xyzvax!user@host
and let xyzvax
worry about it from there.
In summary,
just get the message closer to the destination,
rather than determining the full path.
.sh 4 "Large site, many hosts \*- minimum information"
.pp
Berkeley is an example of a large site,
i.e., more than two or three hosts.
We have decided that the only reasonable philosophy
in our environment
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
they can get away with.
In addition,
any information they do have
should be hints rather than solid information.
.pp
For example,
a typical site on our local ether network is
.q monet.
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
.q ucbvax,
our master host.
Ucbvax may determine that the host name is illegal
and reject the message,
or may be able to do delivery.
However, it is important to note that when a new ethernet host is added,
the only host that
.i must
have its tables updated
is ucbvax;
the others
.i may
be updated as convenient,
but this is not critical.
.pp
This picture is slightly muddied
due to network connections that are not actually located
on ucbvax.
For example,
our TCP connection is currently on
.q ucbarpa.
However,
monet
.i "does not"
know about this;
the information is hidden totally between ucbvax and ucbarpa.
Mail going from monet to a TCP host
is transfered via the ethernet
from monet to ucbvax,
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.
.pp
An interesting point is that it would be possible
to update monet
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
to ucbvax as before.
The only problem that can occur is loops,
as if ucbarpa thought that ucbvax had the TCP connection
and vice versa.
For this reason,
updates should
.i always
happen to the master host first.
.pp
This philosophy results as much from the need
to have a single source for the configuration files
(typically built using
.i m4 \|(1)
or some similar tool)
as any logical need.
Maintaining more than three separate tables by hand
is essentially an impossible job.
.sh 4 "Small site \*- complete information"
.pp
A small site
(two or three hosts)
may find it more reasonable to have complete information
at each host.
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.
.sh 4 "Single host"
.pp
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.
For example,
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.
.sh 3 "Relevant issues"
.pp
The canonical form you use
should almost certainly be as specified in
the Arpanet protocols
RFC819 and RFC822.
Copies of these RFC's are included on the
.i sendmail
tape
as
.i doc/rfc819.lpr
and
.i doc/rfc822.lpr .
.pp
RFC822
describes the format of the mail message itself.
.i Sendmail
follows this RFC closely,
to the extent that many of the standards described in this document
can not be changed without changing the code.
In particular,
the following characters have special interpretations:
.(b
< > ( ) " \e
.)b
Any attempt to use these characters for other than their RFC822
purpose in addresses is probably doomed to disaster.
.pp
RFC819
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.
For example,
at Berkeley
one legal host is
.q a.cc.berkeley.arpa ;
reading from right to left,
.q arpa
is a top level domain
(related to, but not limited to, the physical Arpanet),
.q berkeley
is both an Arpanet host and a logical domain
which is actually interpreted by
a host called ucbvax
(which is actually just the
.q "major"
host for this domain),
.q cc
represents the Computer Center,
(in this case a strictly logical entity),
and
.q a
is a host in the Computer Center;
this particular host happens to be connected
via berknet,
but other hosts might be connected via one of two ethernets
or some other network.
.pp
Beware when reading RFC819
that there are a number of errors in it.
.sh 3 "How to proceed"
.pp
Once you have decided on a philosophy,
it is worth examining the available configuration tables
to decide if any of them are close enough
to steal major parts of.
Even under the worst of conditions,
there is a fair amount of boiler plate that can be collected safely.
.pp
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
to the message.
In particular,
stripping of local domains is best deferred,
since this can leave you with addresses with no domain spec at all.
Since
.i sendmail
likes to append the sending domain to addresses with no domain,
this can change the semantics of addresses.
Also try to avoid
fully qualifying domains in this ruleset.
Although technically legal,
this can lead to unpleasantly and unnecessarily long addresses
reflected into messages.
The Berkeley configuration files
define ruleset nine
to qualify domain names and strip local domains.
This is called from ruleset zero
to get all addresses into a cleaner form.
.pp
Once you have ruleset three finished,
the other rulesets should be relatively trivial.
If you need hints,
examine the supplied configuration tables.
.sh 3 "Testing the rewriting rules \*- the \-bt flag"
.pp
When you build a configuration table,
you can do a certain amount of testing
using the
.q "test mode"
of
.i sendmail .
For example,
you could invoke
.i sendmail
as:
.(b
sendmail \-bt \-Ctest.cf
.)b
which would read the configuration file
.q test.cf
and enter test mode.
In this mode,
you enter lines of the form:
.(b
rwset address
.)b
where
.i rwset
is the rewriting set you want to use
and
.i address
is an address to apply the set to.
Test mode shows you the steps it takes
as it proceeds,
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.
For example:
.(b
1,21,4 monet:bollard
.)b
first applies ruleset three to the input
.q monet:bollard.
Ruleset one is then applied to the output of ruleset three,
followed similarly by rulesets twenty-one and four.
.pp
If you need more detail,
you can also use the
.q \-d21
flag to turn on more debugging.
For example,
.(b
sendmail \-bt \-d21.99
.)b
turns on an incredible amount of information;
a single word address
is probably going to print out several pages worth of information.
.sh 3 "Building mailer descriptions"
.pp
To add an outgoing mailer to your mail system,
you will have to define the characteristics of the mailer.
.pp
Each mailer must have an internal name.
This can be arbitrary,
except that the names
.q local
and
.q prog
must be defined.
.pp
The pathname of the mailer must be given in the P field.
If this mailer should be accessed via an IPC connection,
use the string
.q [IPC]
instead.
.pp
The F field defines the mailer flags.
You should specify an
.q f
or
.q r
flag to pass the name of the sender as a
.b \-f
or
.b \-r
flag respectively.
These flags are only passed if they were passed to
.i sendmail,
so that mailers that give errors under some circumstances
can be placated.
If the mailer is not picky
you can just specify
.q "\-f $g"
in the argv template.
If the mailer must be called as
.b root
the
.q S
flag should be given;
this will not reset the userid
before calling the mailer\**.
.(f
\**\c
.i Sendmail
must be running setuid to root
for this to work.
.)f
If this mailer is local
(i.e., will perform final delivery
rather than another network hop)
the
.q l
flag should be given.
Quote characters
(backslashes and " marks)
can be stripped from addresses if the
.q s
flag is specified;
if this is not given
they are passed through.
If the mailer is capable of sending to more than one user
on the same host
in a single transaction
the
.q m
flag should be stated.
If this flag is on,
then the argv template containing
.b $u
will be repeated for each unique user
on a given host.
The
.q e
flag will mark the mailer as being
.q expensive,
which will cause
.i sendmail
to defer connection
until a queue run\**.
.(f
\**The
.q c
configuration option must be given
for this to be effective.
.)f
.pp
An unusual case is the
.q C
flag.
This flag applies to the mailer that the message is received from,
rather than the mailer being sent to;
if set,
the domain spec of the sender
(i.e., the
.q @host.domain
part)
is saved
and is appended to any addresses in the message
that do not already contain a domain spec.
For example,
a message of the form:
.(b
From: eric@ucbarpa
To: wnj@monet, mckusick
.)b
will be modified to:
.(b
From: eric@ucbarpa
To: wnj@monet, mckusick@ucbarpa
.)b
.i "if and only if"
the
.q C
flag is defined in the mailer corresponding to
.q eric@ucbarpa.
.pp
Other flags are described
in Appendix C.
.pp
The S and R fields in the mailer description
are per-mailer rewriting sets
to be applied to sender and recipient addresses
respectively.
These are applied after the sending domain is appended
and the general rewriting sets
(numbers one and two)
are applied,
but before the output rewrite
(ruleset four)
is applied.
A typical use is to append the current domain
to addresses that do not already have a domain.
For example,
a header of the form:
.(b
From: eric
.)b
might be changed to be:
.(b
From: eric@ucbarpa
.)b
or
.(b
From: ucbvax!eric
.)b
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.
.pp
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
(\er, \en, \ef, \eb)
may be used.
.pp
Finally,
an argv template is given as the E field.
It may have embedded spaces.
If there is no argv with a
.b $u
macro in it,
.i sendmail
will speak SMTP
to the mailer.
If the pathname for this mailer is
.q [IPC],
the argv should be
.(b
IPC $h [ \fIport\fP ]
.)b
where
.i port
is the optional port number
to connect to.
.pp
For example,
the specifications:
.(b
.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
.)b
specifies a mailer to do local delivery
and a mailer for ethernet delivery.
The first is called
.q local,
is located in the file
.q /bin/mail,
takes a picky
.b \-r
flag,
does local delivery,
quotes should be stripped from addresses,
and multiple users can be delivered at once;
ruleset ten
should be applied to sender addresses in the message
and ruleset twenty
should be applied to recipient addresses;
the argv to send to a message will be the word
.q mail,
the word
.q \-d,
and words containing the name of the receiving user.
If a
.b \-r
flag is inserted
it will be between the words
.q mail
and
.q \-d.
The second mailer is called
.q ether,
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
without a domain;
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.
.++ A
.+c "COMMAND LINE FLAGS"
.ba 0
.nr ii 1i
.pp
Arguments must be presented with flags before addresses.
The flags are:
.ip "\-f\ \fIaddr\fP"
The sender's machine address is
.i addr .
This flag is ignored unless the real user
is listed as a
.q "trusted user"
or if
.i addr
contains an exclamation point
(because of certain restrictions in UUCP).
.ip "\-r\ \fIaddr\fP"
An obsolete form of
.b \-f .
.ip "\-h\ \fIcnt\fP"
Sets the
.q "hop count"
to
.i cnt .
This represents the number of times this message has been processed
by
.i sendmail
(to the extent that it is supported by the underlying networks).
.i Cnt
is incremented during processing,
and if it reaches
MAXHOP
(currently 30)
.i sendmail
throws away the message with an error.
.ip \-F\fIname\fP
Sets the full name of this user to
.i name .
.ip \-n
Don't do aliasing or forwarding.
.ip \-t
Read the header for
.q To: ,
.q Cc: ,
and
.q Bcc:
lines, and send to everyone listed in those lists.
The
.q Bcc:
line will be deleted before sending.
Any addresses in the argument vector will be deleted
from the send list.
.ip \-b\fIx\fP
Set operation mode to
.i x .
Operation modes are:
.(b
.ta 4n
m	Deliver mail (default)
a	Run in arpanet mode (see below)
s	Speak SMTP on input side
d	Run as a daemon
t	Run in test mode
v	Just verify addresses, don't collect or deliver
i	Initialize the alias database
p	Print the mail queue
z	Freeze the configuration file
.)b
The special processing for the
ARPANET
includes reading the
.q "From:"
line from the header to find the sender,
printing
ARPANET
style messages
(preceded by three digit reply codes for compatibility with
the FTP protocol
[Neigus73, Postel74, Postel77]),
and ending lines of error messages with <CRLF>.
.ip \-q\fItime\fP
Try to process the queued up mail.
If the time is given,
a sendmail will run through the queue at the specified interval
to deliver queued mail;
otherwise, it only runs once.
.ip \-C\fIfile\fP
Use a different configuration file.
.ip \-d\fIlevel\fP
Set debugging level.
.ip \-o\fIx\|value\fP
Set option
.i x
to the specified
.i value .
These options are described in Appendix B.
.pp
There are a number of options that may be specified as
primitive flags
(provided for compatibility with
.i delivermail ).
These are the e, i, m, and v options.
Also,
the f option
may be specified as the
.b \-s
flag.
.+c "CONFIGURATION OPTIONS"
.pp
The following options may be set using the
.b \-o
flag on the command line
or the
.b O
line in the configuration file:
.nr ii 1i
.ip A\fIfile\fP
Use the named
.i file
as the alias file.
If no file is specified,
use
.i aliases
in the current directory.
.ip a
If set,
wait for an
.q @:@
entry to exist in the alias database
before starting up.
If it does not appear in five minutes,
rebuild the database.
.ip c
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
actually send the mail.
.ip d\fIx\fP
Deliver in mode
.i x .
Legal modes are:
.(b
.ta 4n
i	Deliver interactively (synchronously)
b	Deliver in background (asynchronously)
q	Just queue the message (deliver during queue run)
.)b
.ip D
If set,
rebuild the alias database if necessary and possible.
If this option is not set,
.i sendmail
will never rebuild the alias database
unless explicitly requested
using
.b \-bi .
.ip e\fIx\fP
Dispose of errors using mode
.i x .
The values for
.i x
are:
.(b
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 and give zero exit stat always
.)b
.ip F\fIn\fP
The temporary file mode,
in octal.
644 and 600 are good choices.
.ip f
Save
Unix-style
.q From
lines at the front of headers.
Normally they are assumed redundant
and discarded.
.ip g\fIn\fP
Set the default group id
for mailers to run in
to
.i n .
.ip H\fIfile\fP
Specify the help file
for SMTP.
.ip i
Ignore dots in incoming messages.
.ip L\fIn\fP
Set the default log level to
.i n .
.ip M\fIx\|value\fP
Set the macro
.i x
to
.i value .
This is intended only for use from the command line.
.ip m
Send to me too,
even if I am in an alias expansion.
.ip N
Set the maximum number of connnections that
.i sendmail
will accept simultaneously over an IPC connection
(default four).
This can be used to try to limit the mail load on your system.
Note that this only applies to mail coming in
over an IPC connection,
so that mail submissions occuring from calling
.i sendmail
directly are never restricted.
.ip 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 flag is not on,
only commas delimit names.
Headers are always output with commas between the names.
.ip Q\fIdir\fP
Use the named
.i dir
as the queue directory.
.ip r\fItime\fP
Timeout reads after
.i time
interval.
.ip S\fIfile\fP
Log statistics in the named
.i file .
.ip s
Be super-safe when running things,
i.e.,
always instantiate the queue file,
even if you are going to attempt immediate delivery.
.i Sendmail
always instantiates the queue file
before returning control the the client
under any circumstances.
.ip T\fItime\fP
Set the queue timeout to
.i time .
After this interval,
messages that have not been successfully sent
will be returned to the sender.
.ip t\fIS,D\fP
Set the local timezone name to
.i S
for standard time and
.i D
for daylight time;
this is only used under version six.
.ip u\fIn\fP
Set the default userid for mailers to
.i n .
Mailers without the
.i S
flag in the mailer definition
will run as this user.
.ip v
Run in verbose mode.
.+c "MAILER FLAGS"
The following flags may be set in the mailer description.
.nr ii 4n
.ip f
The mailer wants a
.b \-f
.i from
flag,
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).
.ip r
Same as
.b f ,
but sends a
.b \-r
flag.
.ip S
Don't reset the userid
before calling the mailer.
This would be used in a secure environment
where
.i sendmail
ran as root.
This could be used to avoid forged addresses.
This flag is suppressed if given from an
.q unsafe
environment
(e.g, a user's mail.cf file).
.ip n
Do not insert a UNIX-style
.q From
line on the front of the message.
.ip l
This mailer is local
(i.e.,
final delivery will be performed).
.ip s
Strip quote characters off of the address
before calling the mailer.
.ip m
This mailer can send to multiple users
on the same host
in one transaction.
When a
.b $u
macro occurs in the
.i argv
part of the mailer definition,
that field will be repeated as necessary
for all qualifying users.
.ip F
This mailer wants a
.q From:
header line.
.ip D
This mailer wants a
.q Date:
header line.
.ip M
This mailer wants a
.q Message-Id:
header line.
.ip x
This mailer wants a
.q Full-Name:
header line.
.ip P
This mailer wants a
.q Return-Path:
line.
.ip u
Upper case should be preserved in user names
for this mailer.
.ip h
Upper case should be preserved in host names
for this mailer.
.ip A
This is an Arpanet-compatible mailer,
and all appropriate modes should be set.
.ip U
This mailer wants Unix-style
.q From
lines with the ugly UUCP-style
.q "remote from <host>"
on the end.
.ip e
This mailer is expensive to connect to,
so try to avoid connecting normally;
any necessary connection will occur during a queue run.
.ip X
This mailer want to use the hidden dot algorithm
as specified in RFC821;
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.
.ip L
Limit the line lengths as specified in RFC821.
.ip P
Use the return-path in the SMTP
.q "MAIL FROM:"
command
rather than just the return address;
although this is required in RFC821,
many hosts do not process return paths properly.
.ip I
This mailer will be speaking SMTP
to another
.i sendmail
\*-
as such it can use special protocol features.
This option is not required
(i.e.,
if this option is omitted the transmission will still operate successfully,
although perhaps not as efficiently as possible).
.ip C
If mail is
.i received
from a mailer with this flag set,
any addresses in the header that do not have an at sign
(\c
.q @ )
after being rewritten by ruleset three
will have the
.q @domain
clause from the sender
tacked on.
This allows mail with headers of the form:
.(b
From: usera@hosta
To: userb@hostb, userc
.)b
to be rewritten as:
.(b
From: usera@hosta
To: userb@hostb, userc@hosta
.)b
automatically.
.+c "OTHER CONFIGURATION"
.rm $0
.nr ii 1i
.pp
There are some configuration changes that can be made by
recompiling
.i sendmail .
These are located in three places:
.ip Makefile
Changes in the makefile are operating-system dependent.
These include information about what version of UNIX
you are running, etc.
.ip conf.h
Configuration parameters that may be tweaked by the installer
are included in conf.h.
.ip conf.c
Some special routines and a few variables
may be defined in conf.c.
For the most part these are selected from the settings
in conf.h.
.uh "Changes to the Makefile"
.pp
The following compilation flags may be defined in the makefile
to define the environment in which you are operating.
.ip V6
If set,
this will compile a version 6 system,
with 8-bit user id's,
single character tty id's,
etc.
.ip VMUNIX
If set,
you will be assumed to have a Berkeley 4BSD or 4.1BSD,
including the
.i vfork \|(2)
system call,
special types defined in <sys/types.h>
(e.g, u_char),
etc.
.lp
If none of these flags are set,
a version 7 system is assumed.
.uh "Parameters in conf.h"
.pp
Parameters and compilation options
are defined in conf.h.
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
are their default value.
.nr ii 1.2i
.ip "MAXLINE [256]"
The maximum line length of any input line.
If message lines exceed this length
they will still be processed correctly;
however, header lines,
configuration file lines,
alias lines,
etc.,
must fit within this limit.
.ip "MAXNAME [128]"
The maximum length of any name,
such as a host or a user name.
.ip "MAXFIELD [2500]"
The maximum total length of any header field,
including continuation lines.
.ip "MAXPV [40]"
The maximum number of parameters to any mailer.
This limits the number of recipients that may be passed in one transaction.
.ip "MAXHOP [30]"
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
.b \-h
flag
or by counting the number of trace fields
(i.e,
.q Received:
lines)
in the message header.
.ip "MAXATOM [100]"
The maximum number of atoms
(tokens)
in a single address.
For example,
the address
.q "eric@Berkeley"
is three atoms.
.ip "MAXMAILERS [25]"
The maximum number of mailers that may be defined
in the configuration file.
.ip "MAXRWSETS [30]"
The maximum number of rewriting sets
that may be defined.
.ip "MAXPRIORITIES [25]"
The maximum number of values for the
.q Precedence:
field that may be defined
(using the
.b P
line in sendmail.cf).
.ip "MAXTRUST [30]"
The maximum number of trusted users that may be defined
(using the
.b T
line in sendmail.cf).
.lp
A number of other compilation options exist.
These specify whether or not specific code should be compiled in.
.nr ii 1i
.ip DBM
If set,
the
.q DBM
package in UNIX is used
(see DBM(3X) in [UNIX80]).
If not set,
a much less efficient algorithm for processing aliases is used.
.ip DEBUG
If set, debugging information is compiled in.
To actually get the debugging output,
the
.b \-d
flag must be used.
.ip LOG
If set,
the
.i syslog
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.
.ip QUEUE
This flag should be set to compile in the queueing code.
If this is not set,
mailers must accept the mail immediately
or it will be returned to the sender.
.ip SMTP
If set,
the code to handle user and server SMTP will be compiled in.
This is only necessary if your machine has some mailer
that speaks SMTP.
.ip DAEMON
If set,
code to run a daemon is compiled in.
This code is for 4.2BSD
if the
NVMUNIX
flag is specified;
otherwise,
4.1a BSD code is used.
Beware however
that there are bugs in the 4.1a code
that make it impossible for
.b sendmail
to work correctly
under heavy load.
.ip UGLYUUCP
If you have a UUCP host adjacent to you which is not running
a reasonable version of
.i rmail ,
you will have to set this flag to include the
.q "remote from sysname"
info on the from line.
Otherwise, UUCP gets confused about where the mail came from.
.ip NOTUNIX
If you are using a non-UNIX mail format,
you can set this flag to turn off special processing
of UNIX-style
.q "From "
lines.
.uh "Configuration in conf.c"
.pp
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)
must be specified in the
.i HdrInfo
table in
.i conf.c .
This table contains the header name
(which should be in all lower case)
and a set of header control flags (described below),
The flags are:
.ip H_ACHECK
Normally when the check is made to see if a header line is compatible
with a mailer,
.i sendmail
will not delete an existing line.
If this flag is set,
.i sendmail
will delete
even existing header lines.
That is,
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
sendmail.cf,
the header line is
.i always
deleted.
.ip H_EOH
If this header field 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.
.ip H_FORCE
Add this header entry
even if one existed in the message before.
If a header entry does not have this bit set,
.i sendmail
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.
.ip H_TRACE
If set,
this is a timestamp
(trace)
field.
If the number of trace fields in a message
exceeds a preset amount
the message is returned
on the assumption that it has an aliasing loop.
.ip H_RCPT
If set,
this field contains recipient addresses.
This is used by the
.b \-t
flag to determine who to send to
when it is collecting recipients from the message.
.ip H_FROM
This flag indicates that this field
specifies a sender.
The order of these fields in the
.i HdrInfo
table specifies
.i sendmail's
preference
for which field to return error messages to.
.nr ii 5n
.lp
Let's look at a sample
.i HdrInfo
specification:
.(b
.ta 4n +\w'"return-receipt-to",  'u
struct hdrinfo	HdrInfo[] =
{
	     /* originator fields, most to least significant  */
	"resent-sender",	H_FROM,
	"resent-from",	H_FROM,
	"sender",	H_FROM,
	"from",	H_FROM,
	"full-name",	H_ACHECK,
	     /* destination fields */
	"to",	H_RCPT,
	"resent-to",	H_RCPT,
	"cc",	H_RCPT,
	     /* message identification and control */
	"message",	H_EOH,
	"text",	H_EOH,
	     /* trace fields */
	"received",	H_TRACE|H_FORCE,

	NULL,	0,
};
.)b
This structure indicates that the
.q To: ,
.q Resent-To: ,
and
.q Cc:
fields
all specify recipient addresses.
Any
.q Full-Name:
field will be deleted unless the required mailer flag
(indicated in the configuration file)
is specified.
The
.q Message:
and
.q Text:
fields will terminate the header;
these are specified in new protocols
[NBS80]
or used by random dissenters around the network world.
The
.q Received:
field will always be added,
and can be used to trace messages.
.pp
There are a number of important points here.
First,
header fields are not added automatically just because they are in the
.i HdrInfo
structure;
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
mentioned in the
.i HdrInfo
structure have default processing performed;
that is,
they are added unless they were in the message already.
Second,
the
.i HdrInfo
structure only specifies cliched processing;
certain headers are processed specially by ad hoc code
regardless of the status specified in
.i HdrInfo .
For example,
the
.q Sender:
and
.q From:
fields are always scanned on ARPANET mail
to determine the sender;
this is used to perform the
.q "return to sender"
function.
The
.q "From:"
and
.q "Full-Name:"
fields are used to determine the full name of the sender
if possible;
this is stored in the macro
.b $x
and used in a number of ways.
.pp
The file
.i conf.c
also contains the specification of ARPANET reply codes.
There are four classifications these fall into:
.(b
.sz -1
.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 */
.sz
.)b
The class
.i Arpa_Info
is for any information that is not required by the protocol,
such as forwarding information.
.i Arpa_TSyserr
and
.i Arpa_PSyserr
is printed by the
.i syserr
routine.
TSyserr
is printed out for transient errors,
whereas PSyserr
is printed for permanent errors;
the distinction is made based on the value of
.i errno .
Finally,
.i Arpa_Usrerr
is the result of a user error
and is generated by the
.i usrerr
routine;
these are generated when the user has specified something wrong,
and hence the error is permanent,
i.e.,
it will not work simply by resubmitting the request.
.pp
If it is necessary to restrict mail through a relay,
the
.i checkcompat
routine can be modified.
This routine is called for every recipient address.
It can return
.b TRUE
to indicate that the address is acceptable
and mail processing will continue,
or it can return
.b FALSE
to reject the recipient.
If it returns false,
it is up to
.i checkcompat
to print an error message
(using
.i usrerr )
saying why the message is rejected.
For example,
.i checkcompat
could read:
.(b
.re
.sz -1
.ta 4n +4n +4n +4n +4n +4n +4n
bool
checkcompat(to)
	register ADDRESS *to;
{
	if (MsgSize > 50000 && to->q_mailer != LocalMailer)
	{
		usrerr("Message too large for non-local delivery");
		NoReturn = TRUE;
		return (FALSE);
	}
	return (TRUE);
}
.sz
.)b
This would reject messages greater than 50000 bytes
unless they were local.
The
.i NoReturn
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
implementation,
and use should be limited.
.+c "SUMMARY OF SUPPORT FILES"
.pp
This is a summary of the support files
that
.i sendmail
creates or generates.
.nr ii 1i
.ip "/usr/lib/sendmail"
The binary of
.i sendmail .
.ip /usr/bin/newaliases
A link to /usr/lib/sendmail;
causes the alias database to be rebuilt.
Running this program is completely equivalent to giving
.i sendmail
the
.b \-bi
flag.
.ip /usr/bin/mailq
Prints a listing of the mail queue.
This program is equivalent to using the
.b \-bp
flag to
.i sendmail .
.ip /usr/lib/sendmail.cf
The configuration file,
in textual form.
.ip /usr/lib/sendmail.fc
The configuration file
represented as a memory image.
.ip /usr/lib/sendmail.hf
The SMTP help file.
.ip /usr/lib/sendmail.st
A statistics file; need not be present.
.ip /usr/lib/aliases
The textual version of the alias file.
.ip /usr/lib/aliases.{pag,dir}
The alias file in
.i dbm \|(3)
format.
.ip /etc/syslog
The program to do logging.
.ip /etc/syslog.conf
The configuration file for syslog.
.ip /etc/syslog.pid
Contains the process id of the currently running syslog.
.ip /usr/spool/mqueue
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*
Data files.
.ip /usr/spool/mqueue/lf*
Lock files
.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.
.ro
.ls 1
.tp
.sp 2i
.in 0
.ce 100
.sz 24
.b SENDMAIL
.sz 14
.sp
INSTALLATION AND OPERATION GUIDE
.sp
.sz 10
Eric Allman
Britton-Lee, Inc.
.sp
Version 3.18
.sp 2
.sz 14
DRAFT
.ce 0
.bp 1
.ce
.sz 12
TABLE OF CONTENTS
.sz 10
.sp 2
.\" remove some things to avoid "out of temp file space" problem
.rm sh
.rm (x
.rm )x
.rm ip
.rm pp
.rm lp
.rm he
.rm fo
.rm eh
.rm oh
.rm ef
.rm of
.xp