PROCMAIL

NAME

procmail - autonomous mail processor

SYNOPSIS

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

DESCRIPTION

For a quick start, see NOTES at the end.

Procmail should be invoked automatically over the .forward file mechanism as soon as mail arrives. Alternatively, when installed by a system administrator, 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 arguments 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 distributed 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, backwards compatible mail delivery agent.

Procmail can also be used as a general purpose mail filter, 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

OPTIONS

-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).

-a argument

This will set $1 to be equal to argument. 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.

-d recipient ...

This turns on explicit delivery mode, delivery will be to the local user recipient. This, of course, only is possible if procmail has root privileges (or if procmail is already running with the recipient’s euid and egid). Procmail will setuid to the intended recipients and delivers the mail as if it were invoked by the recipient with no arguments (i.e. if no rcfile is found, delivery is like ordinary mail). This option is incompatible with -p.

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 sendmail.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:

:0 # sink all junk mail
* ^Subject:.*junk
/dev/null

:0 # pass along all other mail
! -oi -f "$@"

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

/var/mail/$LOGNAME.lock

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

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

Autoforwarding mailbox found

The system mailbox had its suid or sgid bit set, procmail terminates with EX_NOUSER assuming that this mailbox must not be delivered to.

Bad substitution of "x"

Not a valid environment variable name specified.

Closing brace unexpected

There was no corresponding opening brace (nesting block).

Conflicting x suppressed

Flag x is not compatible with some other flag on this recipe.

Couldn’t determine implicit lockfile from "x"

There were no ’>>’ redirectors to be found, using simply ’$LOCKEXT’ as locallockfile.

Deadlock attempted on "x"

The locallockfile specified on this recipe is equal to a still active $LOCKFILE.

Denying special privileges for "x"

Procmail will not take on the identity that comes with the rcfile because a security violation was found (e.g. -p or variable assignments on the command line) or procmail had insufficient privileges to do so.

Enforcing stricter permissions on "x"

The system mailbox of the recipient was found to be unsecured, procmail secured it.

Error while writing to "x"

Nonexistent subdirectory, no write permission, pipe died or disk full.

Excessive output quenched from "x"

The program or filter "x" tried to produce too much output for the current LINEBUF, the rest was discarded.

Forced unlock denied on "x"

No write permission in the directory where lockfile "x" resides, or more than one procmail trying to force a lock at exactly the same time.

Insufficient privileges

Procmail either needs root privileges, or must have the right (e)uid and (e)gid to run in delivery mode. The mail will bounce.

No space left to finish writing "x"

The filesystem containing "x" does not have enough free space to permit delivery of the message to the file.

Program failure (nnn) of "x"

Program that was started by procmail returned nnn instead of EXIT_SUCCESS (=0); if nnn is negative, then this is the signal the program died on.

Renaming bogus "x" into "x"

The system mailbox of the recipient was found to be bogus, procmail performed evasive actions.

Terminating prematurely whilst waiting for ...

Procmail received a signal while it was waiting for ...

Quota exceeded while writing "x"

The filesize quota for the recipient on the filesystem containing "x" does not permit delivering the message to the file.

Timeout, terminating "x"

Timeout has occurred on program or filter "x".

Timeout, was waiting for "x"

Timeout has occurred on program, filter or file "x". If it was a program or filter, then it didn’t seem to be running anymore.

Truncated file to former size

The file could not be delivered to successfully, so the file was truncated to its former size.

Truncating "x" and retrying lock

"x" does not seem to be a valid filename or the file is not empty.

Rescue of unfiltered data succeeded/failed

A filter returned unsuccessfully, procmail tried to get back the original text.

EXTENDED DIAGNOSTICS

Extended diagnostics can be turned on and off through setting the VERBOSE variable.

Assuming identity of the recipient, VERBOSE=off

Dropping all privileges (if any), implicitly turns off extended diagnostics.

Notified comsat: "$LOGNAME@offset:file"

Sent comsat/biff a notice that mail arrived for user $LOGNAME at ’offset’ in ’file’.

Reiterating kernel-lock

While attempting several locking methods, one of these failed. Procmail will reiterate until they all succeed in rapid succession.

Score: added newtotal "x"

This condition scored ’added’ points, which resulted in a ’newtotal’ score.

WARNINGS

You should create a shell script that uses lockfile(1) before invoking your mail shell on any mailbox file other than 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.

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.

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 #uid and SHELL will default to /bin/sh.

When in explicit delivery mode, procmail will generate a leading ’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 either owned by the recipient or root and not world writable, or if the directory it is contained in is not world writable.

If /var/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.’ 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/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 (or to MH 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: fcntl(2).

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 <nancym@ii.com> 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 it must be an absolute path. The #YOUR_USERNAME is not actually a parameter that is required by procmail, in fact, it will be discarded by sh before procmail ever sees it; it is however a necessary kludge against overoptimising sendmail programs:

"|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/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 (v3.11pre7 1997/04/28) available at your nearest USENET comp.sources.misc archive, or at ftp.informatik.rwth-aachen.de as pub/packages/procmail/procmail.tar.gz.

MAILINGLIST

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

<procmail@informatik.rwth-aachen.de>

for submitting questions/answers.

<procmail-request@informatik.rwth-aachen.de>

for subscription requests.

If you would like to stay informed about new versions and official patches send a subscription request to

procmail-announce-request@informatik.rwth-aachen.de

(this is a readonly list).

AUTHOR

Stephen R. van den Berg

<srb@cuci.nl>