Procmail

Synopsis
procmail [-ptoY] [-f fromwhom]
[parameter=value | rcfile] ...
procmail [-toY] [-f fromwhom] [-a argument] ...
-d recipient ...
procmail [-ptY] -m [parameter=value] ... rcfile
[argument] ...
procmail [-toY] [-a argument] -z
procmail -v

Description
Procmail should be invoked automatically over the .forward file mechanism as soon as mail arrives. Alternatively, when installed by a system administrator (and in the standard Red Hat Linux configuration), it can be invoked from within the mailer immediately. When invoked, it first sets some environment variables to default values, reads the mail message from stdin until an EOF, separates the body from the header, and then, if no command line argu­ ments are present, it starts to look for a file named $HOME/.procmailrc. According to the processing recipes in this file, the mail message that just arrived gets dis­ tributed into the right folder (and more). If no rcfile is found, or processing of the rcfile falls off the end, procmail will store the mail in the default system mailbox.

If no rcfiles and no -p have been specified on the command line, procmail will, prior to reading $HOME/.procmailrc, interpret commands from /etc/procmailrc (if present). Care must be taken when creating /etc/procmailrc, because, if circumstances permit, it will be executed with root privileges (contrary to the $HOME/.procmailrc file of course).

If running suid root or with root privileges, procmail will be able to perform as a functionally enhanced, back­ wards compatible mail delivery agent.

Procmail can also be used as a general purpose mail fil­ ter, i.e., provisions have been made to enable procmail to be invoked in a special sendmail rule.

The rcfile format is described in detail in the procmailrc(5) man page. The weighted scoring technique is described in detail in the procmailsc(5) man page.

Examples for rcfile recipes can be looked up in the procmailex(5) man page.

Signals

TERMINATE Terminate prematurely and requeue the mail.

HANGUP Terminate prematurely and bounce the mail.

INTERRUPT Terminate prematurely and bounce the mail.

QUIT Terminate prematurely and silently lose the mail.

ALARM Force a timeout (see TIMEOUT).

USR1 Equivalent to a VERBOSE=off.

USR2 Equivalent to a VERBOSE=on.

 

Options
-v
Procmail will print its version number, display its compile time configuration and exit.

-p
Preserve any old environment. Normally procmail clears the environment upon startup, except for the value of TZ. However, in any case: any default values will override any preexisting environment variables, i.e., procmail will not pay any attention to any predefined environment variables, it will happily overwrite them with its own defaults. For the list of environment variables that procmail will preset see the procmailrc(5) man page. If both -p and -m are specified, the list of preset environment variables shrinks to just: LOGNAME, HOME, SHELL, ORGMAIL and MAILDIR.

-t
Make procmail fail softly, i.e., if procmail cannot deliver the mail to any of the destinations you gave, the mail will not bounce, but will return to the mailqueue. Another delivery-attempt will be made atsome time in the future.

-f fromwhom
Causes procmail to regenerate the leading `From 'line with fromwhom as the sender (instead of -f one could use the alternate and obsolete -r). If fromwhom consists merely of a single `-', then procmail will only update the timestamp on the `From ' line (if present, if not, it will generate a new one).

-o
Instead of allowing anyone to generate `From ' lines,simply override the fakes.

-Y
Assume traditional Berkeley mailbox format, ignore any Content-Length: fields.

-a argument
This will set $1 to be equal to argument. Each succeeding -a argument will set the next number variable ($2, $3, etc). It can be used to pass meta information along to procmail. This is typically done by passing along the $@x information from the sendmail mailer rule.

-m
Turns procmail into a general purpose mail filter. In this mode one rcfile must be specified on the command line. After the rcfile, procmail will accept an unlimited number of arguments. If the rcfile is an absolute path starting with /etc/procmailrcs/ without backward references (i.e. the parent directory cannot be mentioned) procmail will, only if no security violations are found, take on the identity of the owner of the rcfile (or symbolic link). For some advanced usage of this option you should look in the EXAMPLES section below.

-z
This turns on LMTP mode, wherein procmail acts as an RFC2033 LMTP server. Delivery takes place in the same manner and under the same restrictions as the delivery mode enabled with -d. This option is incompatible with -p and -f.

Arguments
Any arguments containing an '=' are considered to be environment variable assignments, they will all be evaluated after the default values have been assigned and before the first rcfile is opened. Any other arguments are presumed to be rcfile paths (either absolute, or if they start with `./' relative to the current directory; any other relative path is relative to $HOME, unless the -m option has been given, in which case all relative paths are relative to the current directory); procmail will start with the first one it finds on the command line. The following ones will only be parsed if the preceding ones have a not matching HOST-directive entry, or in case they should not exist.

If no rcfiles are specified, it looks for $HOME/.procmailrc. If not even that can be found, processing will continue according to the default settings of the environment variables and the ones specified on the command line.

Examples
Examples for rcfile recipes can be looked up in the procmailex(5) man page. A small sample rcfile can be found in the NOTES section below.

Skip the rest of this EXAMPLES section unless you are a system administrator who is vaguely familiar with send-mail.cf syntax.

The -m option is typically used when procmail is called from within a rule in the sendmail.cf file. In order to be able to do this it is convenient to create an extra `procmail' mailer in your sendmail.cf file (in addition to the perhaps already present `local' mailer that starts up procmail). To create such a `procmail' mailer I'd suggest something like:

Mprocmail, P=/usr/bin/procmail, F=mSDFMhun, S=11, R=21,
A=procmail -m $h $g $u

This enables you to use rules like the following (most likely in ruleset 0) to filter mail through the procmail mailer (please note the leading tab to continue the rule, and the tab to separate the comments):

R$*<@some.where>$*

$#procmail $@/etc/procmailrcs/some.rc $:$1@some.where.procmail$2

R$*<@$*.procmail>$*

$1<@$2>$3 Already filtered, map back

And /etc/procmailrcs/some.rc could be as simple as:

SENDER = "<$1>" # fix for empty sender addresses

SHIFT = 1 # remove it from $@

:0 # sink all junk mail

* ^Subject:.*junk

/dev/null

:0 w # pass along all other mail

! -oi -f "$SENDER" "$@"

Do watch out when sending mail from within the /etc/procmailrcs/some.rc file, if you send mail to addresses which match the first rule again, you could be creating an endless mail loop.

Files
/etc/passwd
to set the recipient's LOGNAME, HOME and SHELL variable defaults

/var/spool/mail/$LOGNAME
system mailbox; both the system mailbox and the immediate directory it is in will be created every time procmail starts and either one is not present

/etc/procmailrc
initial global rcfile

/etc/procmailrcs/
special privileges path for rcfiles

$HOME/.procmailrc
default rcfile

/var/spool/mail/$LOGNAME.lock
lockfile for the system mailbox (not automatically used by procmail, unless $DEFAULT equals /var/spool/mail/$LOGNAME and procmail is delivering to $DEFAULT)

/usr/sbin/sendmail
default mail forwarder

_????`hostname`
temporary `unique' zero-length files created by procmail

See Also
procmailrc(5), procmailsc(5), procmailex(5), sh(1), csh(1), mail(1), mailx(1), binmail(1), uucp(1), aliases(5), sendmail(8), egrep(1), grep(1), biff(1), comsat(8), lockfile(1), formail(1), cron(1)

Diagnostics

Extended Diagnostics

Warning
You should create a shell script that uses lockfile(1) before invoking your mail shell on any mailbox file otherthan the system mailbox (unless of course, your mail shell uses the same lockfiles (local or global) you specified in your rcfile).

In the unlikely event that you absolutely need to kill procmail before it has finished, first try and use the regular kill command (i.e., not kill -9, see the subsection Signals for suggestions), otherwise some lockfiles might not get removed.

Beware when using the -t option, if procmail repeatedly is unable to deliver the mail (e.g., due to an incorrect rcfile), the system mailqueue could fill up. This could aggravate both the local postmaster and other users.

The /etc/procmailrc file might be executed with root privileges, so be very careful of what you put in it. SHELL will be equal to that of the current recipient, so if procmail has to invoke the shell, you'd better set it to some safe value first. See also: DROPPRIVS.

Keep in mind that if chown(1) is permitted on files in /etc/procmailrcs/, that they can be chowned to root (or anyone else) by their current owners. For maximum security, make sure this directory is executable to root only.

Procmail is not the proper tool for sharing one mailbox among many users, such as when you have one POP account for all mail to your domain. It can be done if you manage to configure your MTA to add some headers with the envelope recipient data in order to tell Procmail who a message is for, but this is usually not the right thing to do. Perhaps you want to investigate if your MTA offers `virtual user tables', or see check out the `multidrop' facility of Fetchmail.

Bugs
After removing a lockfile by force, procmail waits $SUSPEND seconds before creating a new lockfile so that another process that decides to remove the stale lockfile will not remove the newly created lock by mistake.

Procmail uses the regular TERMINATE signal to terminate any runaway filter, but it does not check if the filter responds to that signal and it only sends it to the filter itself, not to any of the filter's children.

A continued Content-Length: field is not handled correctly.

The embedded newlines in a continued header should be skipped when matching instead of being treated as a single space as they are now.

Miscellaneous
If there is an existing Content-Length: field in the header of the mail and the -Y option is not specified, procmail will trim the field to report the correct size. Procmail does not change the fieldwidth.

If there is no Content-Length: field or the -Y option has been specified and procmail appends to regular mailfolders, any lines in the body of the message that look like postmarks are prepended with `>' (disarms bogus mailheaders). The regular expression that is used to search for these postmarks is: `\nFrom '

If the destination name used in explicit delivery mode is not in /etc/passwd, procmail will proceed as if explicit delivery mode was not in effect. If not in explicit delivery mode and should the uid procmail is running under, have no corresponding /etc/passwd entry, then HOME will default to /, LOGNAME will default to the numeric uid, SHELL will default to /bin/sh, and ORGMAIL will default to /tmp/dead.letter.

When in explicit delivery mode, procmail will generate aleading `From ' line if none is present. If one is already present procmail will leave it intact. If procmail is not invoked with one of the following user or group ids: root, daemon, uucp, mail, x400, network, list, slist, lists or news, but still has to generate or accept a new `From ' line, it will generate an additional `>From ' line to help distinguish fake mails.

For security reasons procmail will only use an absolute or $HOME-relative rcfile if it is owned by the recipient or root, not world writable, and the directory it is contained in is not world writable. The $HOME/.procmailrc file has the additional constraint of not being group-writable or in a group-writable directory.

If /var/spool/mail/$LOGNAME is a bogus mailbox (i.e., does not belong to the recipient, is unwritable, is a symbolic link or is a hard link), procmail will upon startup try to rename it into a file starting with `BOGUS.$LOGNAME.' and ending in an inode-sequence-code. If this turns out to be impossible, ORGMAIL will have no initial value, and hence will inhibit delivery without a proper rcfile.

If /var/spool/mail/$LOGNAME already is a valid mailbox, but has got too loose permissions on it, procmail will correct this. To prevent procmail from doing this make sure the u+x bit is set.

When delivering to directories, MH folders, or maildir folders, you don't need to use lockfiles to prevent several concurrently running procmail programs from messing up.

Delivering to MH folders is slightly more time consuming than delivering to normal directories or mailboxes, because procmail has to search for the next available number (instead of having the filename immediately available).

On general failure procmail will return EX_CANTCREAT, unless option -t is specified, in which case it will return EX_TEMPFAIL.

To make `egrepping' of headers more consistent, procmail concatenates all continued header fields; but only internally. When delivering the mail, line breaks will appear as before.

If procmail is called under a name not starting with `procmail' (e.g., if it is linked to another name and invoked as such), it comes up in explicit delivery mode, and expects the recipients' names as command line arguments (as if -d had been specified).

Comsat/biff notifications are done using udp. They are sent off once when procmail generates the regular logfile entry. The notification messages have the following extended format (or as close as you can get when final delivery was not to a file):

$LOGNAME@offset_of_message_in_mailbox:absolute_path_to_mailbox

Whenever procmail itself opens a file to deliver to, it consistently uses the following kernel locking strategies: lockf(3).

Procmail is NFS-resistant and eight-bit clean.

Notes
Calling up procmail with the -h or -? options will cause it to display a command-line help and recipe flag quick reference page.

There exists an excellent newbie FAQ about mailfilters (and procmail in particular); it is being maintained by Nancy McGough and can be obtained by sending a mail to mail-server@rtfm.mit.edu with the following in the body:

send usenet/news.answers/mail/filtering-faq

Instead of using the system provided invocation of procmail when mail arrives, you can control the invocation of procmail yourself. In this case your $HOME/.forward (beware, it has to be world readable) file should contain the line below. Be sure to include the single and double quotes, and unless you know your site to be running smrsh (the SendMail Restricted SHell), it must be an absolute path.

"|exec /usr/bin/procmail"

Procmail can also be invoked to postprocess an already filled system mailbox. This can be useful if you don't want to or can't use a $HOME/.forward file (in which case the following script could periodically be called from within cron(1), or whenever you start reading mail):

#!/bin/sh
ORGMAIL=/var/spool/mail/$LOGNAME
if cd $HOME &&
test -s $ORGMAIL &&
lockfile -r0 -l1024 .newmail.lock 2>/dev/null
then
trap "rm -f .newmail.lock" 1 2 3 13 15
umask 077
lockfile -l1024 -ml
cat $ORGMAIL >>.newmail &&
cat /dev/null >$ORGMAIL
lockfile -mu
formail -s procmail <.newmail &&
rm -f .newmail
rm -f .newmail.lock
fi

exit 0

A sample small $HOME/.procmailrc:

PATH=/bin:/usr/bin:/usr/bin|
MAILDIR=$HOME/Mail #you'd better make sure it exists
DEFAULT=$MAILDIR/mbox #completely optional
LOGFILE=$MAILDIR/from #recommended
:0:
* ^From.*berg
from_me
:0
* ^Subject:.*Flame
/dev/null

Other examples for rcfile recipes can be looked up in the procmailex(5) man page.

Source
This program is part of the procmail mail-processing-package (v3.21) available at http://www.procmail.org/ or ftp.procmail.org in pub/procmail/.

Mailing List
There exists a mailinglist for questions relating to any program in the procmail package:

for submitting questions/answers.
for subscription requests.

If you would like to stay informed about new versions and official patches send a subscription request to procmail-announce-request@procmail.org (this is a read only list).

Authors
Stephen R. van den Berg
Philip A. Guenther