Procmail Frequently Asked Questions

This is the original FAQ which comes with the Procmail distribution. I have included it here in order to make it easy to reference it from my own attempt at a Procmail FAQ

I have made every attempt to preserve as much as possible of Stephen's original FAQ. The HTML encoding is by me, though.

If you want to check out the original, text-only version, look no further.

$Id: faq.html,v 1.2 2009/01/07 12:04:02 gsutter Exp $

Table of Contents

1. How do I go about setting up a mailinglist or a mail-archive server?
2. I installed procmail (i.e. typed 'make install'), but how am I supposed to use it? When I type procmail on the command line it simply does nothing.
3. When I compile everything the compiler complains about invalid or illegal pointer combinations, but it produces the executables anyway. Should I be concerned?
4. The compiler seems to issue warnings about "loop not entered at top", is that a problem?
5. The compiler complains about unmodifiable lvalues or assignments to const variables. Now what?
6. The compiler refuses to compile regexp.c, what is the problem?
7. Everything installed just fine, it's just that there are several stale _locktst processes which refuse to die. How do I get rid of those?
8. When I send myself a testmail, the mail bounces with the message: cannot execute binary file. What am I doing wrong?
9. Where do I look for examples about:
   • One home directory, several machine architectures?
   • Procmail as an integrated local mail delivery agent? (generic, sendmail, ZMailer, smail, SysV mailsurr)
   • Changing the mail spool directory to $HOME for all users
   • Security considerations (when installing procmail suid root)
10. How do I use procmail as a general mail filter inside sendmail?
11. Why do I have to insert my login name after the '#' in the .forward or .maildelivery file?
12. How do I view the man pages?
13. The leading From_ line on all my arriving mail shows the wrong time. Before putting procmail in the .forward file everything was OK.
14. When sending mail to someone with procmail in his/her .forward I sometimes get back an error saying: "Cannot mail directly to programs."
15. When sending mail to someone with procmail in his/her .forward I sometimes get back an error saying: "User doesn't have a valid shell for mailing to programs."
16. My mailtool sometimes reports that it is confused about the state of the mailbox, or I get "Couldn't unlock" errors from procmail now and then, or sometimes it simply seems to hang just when new mail arrives.
17. I sometimes get these `Lock failure on "/usr/mail/$LOGNAME.lock"' errors from procmail. What do I do about it?
18. None of the above topics cover my problem. Should I panic?

Frequently Asked Questions

1. How do I go about setting up a mailinglist or a mail-archive server?
   Look in the SmartList directory, start reading the INTRO file, it describes it in detail and should get you started.
2. I installed procmail (i.e. typed 'make install'), but how am I supposed to use it? When I type procmail on the command line it simply does nothing.
   

   ---

   
   There exists an excellent newbie FAQ about mailfilters (and procmail in particular), it is being maintained by Nancy McGough and can be obtained via:
   World Wide Web (the nicest format for online reading!):
   http://www.cis.ohio-state.edu/hypertext/faq/usenet/mail/filtering-faq/faq.html
   (If the above doesn't work, try the "FAQ Launcher" at http://www.ii.com/internet/faqs/launchers/mail/filtering-faq/ ... Thanks to Eric Hilding for pointing out this problem. // era)
   Anonymous FTP:
   ftp://rtfm.mit.edu/pub/usenet/news.answers/mail/filtering-faq
   Email:
   Send mail to mail-server@rtfm.mit.edu containing the following:
   

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

   
   UUCP:
   

   uunet!/archive/usenet/news.answers/mail/filtering-faq
   

   
   It is also posted monthly in at least the following newsgroups:
   comp.mail.misc, comp.answers, news.answers
   

   ---

   
   You're not supposed to start procmail from the command line. Procmail expects exactly one mail message to be presented to it on its stdin. Usually the mail system feeds it into procmail. If you start it by hand, you have to type the mail.
   Be sure to have a .forward and a .procmailrc file in your home directory (see the examples subdirectory or the man page). MMDF users should note that they need a .maildelivery file instead of a .forward file (see the man page for more detailed information).
   If however, procmail has been integrated in the maildelivery system (i.e. if your system administrator installed it that way, ask him/her), then you no longer need the .forward files in your home directory, having a .procmailrc file will suffice.
   On some systems .forward files are not checked. It might be possible that your system supports a command like:

   mail -F "|/usr/local/bin/procmail"
   

   to set up forwarding to a program. If that doesn't seem to work it might be worth trying to put a line looking like this:

   Forward to |/usr/local/bin/procmail
   

   or if that doesn't work, try:

   Pipe to /usr/local/bin/procmail
   

   as the only line in your mail spool file (e.g. /usr/mail/$LOGNAME), as well as doing a chmod 06660 /usr/mail/$LOGNAME. For more information on such systems, do a "man mail".
   If all of this doesn't work, procmail can be called on a periodical basis, either via "cron", "at" or whenever you start reading mail (or log in). For a sample script look in the NOTES section of the procmail(1) man page.
3. When I compile everything the compiler complains about invalid or illegal pointer combinations, but it produces the executables anyway. Should I be concerned?
   Ignore these warnings, they simply indicate that either your compiler or your system include files are not ANSI/POSIX compliant. The compiler will produce correct code regardless of these warnings.
4. The compiler seems to issue warnings about "loop not entered at top", is that a problem?
   No, no problem at all, it just means I wrote the code :-). That's just about the only uncommon coding technique I use (don't think I don't try to avoid those jumps in loops, it's just that sometimes they are the best way to code it). Use gcc if you want to avoid these warnings.
5. The compiler complains about unmodifiable lvalues or assignments to const variables. Now what?
   Well, if the compiler produces the executables anyway everything probably is all right. If it doesn't, you might try inserting a #define const in the autoconf.h file by hand. However in any case, your compiler is broken; I would recommend submitting this as a compiler bug to your vendor. In any case, if this should occur, I'd appreciate a mail from you (so I can try to fix the autoconf script to recognise your compiler correctly as well).
6. The compiler refuses to compile regexp.c, what is the problem?
   Try compiling that module with optimisation turned off.
7. Everything installed just fine, it's just that there are several stale _locktst processes which refuse to die. How do I get rid of those?
   In order to prevent things like this from happening to procmail, _locktst tries to determine which kernel locking methods are reliable. Sometimes this triggers a bug in the kernel or in your system-supplied lockd; this is good, because _locktst detects this and makes sure that procmail will not make the same mistake. A side effect is that this sometimes leaves behind some stale _locktst processes that seem to be unkillable.
   This usually is the result of a buggy lockdaemon. In order to get rid of the stale processes, ask your system administrator to kill and restart the (rpc.)lockd (and perhaps the (rpc.)statd) on both the filesystem-client (where you compiled procmail) and the filesystem-server(s) (where the lockingtests took place). Depending on the OS it might help if you send the offending _locktst processes a kill signal before or after restarting the lockd again.
   In any case, _locktst just uncovered a bug in your operating system. You should contact your system's vendor and ask for a bugfix for your lockd.
8. When I send myself a testmail, the mail bounces with the message: cannot execute binary file. What am I doing wrong?
   It is very well possible that mail is processed on a different machine from that where you usually read your mail. Therefore you have to make sure that procmail has the right binary format to execute on those machines on which mail could arrive. In order to get this right you might need to do some .forward file tweaking, look at the examples/advanced file for some suggestions.
9. Where do I look for examples about:
   • One home directory, several machine architectures?
   • Procmail as an integrated local mail delivery agent? (generic, sendmail, ZMailer, smail, SysV mailsurr)
   • Changing the mail spool directory to $HOME for all users
   • Security considerations (when installing procmail suid root)
   
   Well, this probably is your lucky day :-), all these topics are covered in the examples / advanced file.
   Other examples (e.g. for autoreplies) are most likely to be found by typing: man procmailex
10. How do I use procmail as a general mail filter inside sendmail?
    See EXAMPLES section of the procmail(1) man page.
11. Why do I have to insert my login name after the '#' in the .forward or .maildelivery file?
    Some mailers `optimise' maildelivery and take out duplicates from Cc:, Bcc: and alias lists before delivery. If two or more persons on such a list would have identical .forward files, then the mailer will eliminate all but one. Adding a `#' with your login name following it will make the .forward files unique, and will ensure that the mailer doesn't optimise away some addresses.
12. How do I view the man pages?
    If the man(1) program on your system understands the MANPATH environment variable, make sure that the installation directory listed in the Makefile for the manpages is included in your MANPATH. If your man program does not support MANPATH, make sure that the man pages are installed in one of the standard man directories, like under /usr/man. If you do not want to install the man pages before viewing them, you can view an individual man file by typing something like:

    nroff -man procmail.1 | more
    

13. The leading From_ line on all my arriving mail shows the wrong time. Before putting procmail in the .forward file everything was OK.
    This is a known bug in sendmail-5.65c+IDA. The real fix would be to upgrade to sendmail 6.x or later. For a quick fix, see the procmailex man page.
14. When sending mail to someone with procmail in his/her .forward I sometimes get back an error saying: "Cannot mail directly to programs."
    This is a known bug in some older sendmails that mistakenly drop their root privileges when they are given the -t flag. Either make sure that your sendmail always forwards to a mailserver first or upgrade to sendmail 6.x or later.
15. When sending mail to someone with procmail in his/her .forward I sometimes get back an error saying: "User doesn't have a valid shell for mailing to programs."
    This indicates that the mail arrives on a mailserver which most likely has a different user database (/etc/passwd) where the login shell specified for the recipient is not present in /etc/shells. Contact your administrator to put the name of that shell in /etc/shells.
16. My mailtool sometimes reports that it is confused about the state of the mailbox, or I get "Couldn't unlock" errors from procmail now and then, or sometimes it simply seems to hang just when new mail arrives.
    This is a known bug in the OpenLook mailtool. It holds on to the kernel lock on the mail-spoolfile most of the time, and releases this lock when it shouldn't. Either ask for a bugfix from your vendor (I'm not sure if a bugfix exists), or make sure that during the compilation of procmail both the fcntl() and lockf() locking methods are disabled (see config.h).
17. I sometimes get these `Lock failure on "/usr/mail/$LOGNAME.lock"' errors from procmail. What do I do about it?
    The problem here is that as long as procmail has not read a $HOME/.procmailrc file, it can hang on to the sgid mail permission (which it needs in order to create a lockfile in /usr/mail). I.e. if procmail delivers mail to a user without a $HOME/.procmailrc file, procmail can (and does) use the /usr/mail/$LOGNAME.lock file.
    If, however, it finds a $HOME/.procmailrc file, procmail has to let go of the sgid mail permission because otherwise any ordinary user could abuse that.
    There are several solutions to this problem:
    • Some systems support the sticky bit on directories (when set only allows the owner of a file in that directory to rename or remove it). This enables you to make /usr/spool/mail drwxrwxrwt. It is thus effectively world writable, but all the mailboxes in it are protected because only the mailbox owner can remove or rename it.
    • If your system did not exhibit the !@#$%^&* POSIX semantics for setgid(), procmail would have been able to switch back and forth between group mail and the group the recipient belongs to without creating security holes.
    • If your system supported setrgid() or setregid() or setresgid() with BSD semantics, procmail would have been able to switch... (see the previous point).
    • You could simply put the following at the end of your .procmailrc file:

      LOCKFILE		# removes any preexisting lockfile
      LOG=`lockfile $DEFAULT$LOCKEXT`
      TRAP="rm -f $DEFAULT$LOCKEXT"
      :0
      $DEFAULT
      

    • You could, instead of using /usr/mail/$LOGNAME, use a file below your home directory as your default mailbox.
    • Or, you could still use /usr/mail/$LOGNAME as the mailbox, but simply instruct procmail to use a different lockfile. This can be achieved by putting following recipe at the bottom of your .procmailrc file:

      :0:$HOME/.lockmail
      $DEFAULT
      

      You have to make sure that all other programs that update your system mailbox will be using the same lockfile of course.
    • You can ignore the problem if you know that both your mail reader and procmail use an overlapping kernel locking method.
18. None of the above topics cover my problem. Should I panic?
    Let me ask you a question :-), have you examined the CAVEATS, WARNINGS, BUGS and NOTES sections of the manual pages closely? If you have, well, then panic. Or, alternatively, you could submit your question to the procmail mailinglist (see the man page for the exact addresses, or try "procmail -v", or look in the patchlevel.h file).