Date: Sun, 11 Mar 2001 10:27:24 -0800

  The list currently includes slocal (included with MH), deliver,
  procmail and mailagent. They are briefly described here. Slocal is
  probably the most popular by virtue of being included in the
  distribution. The next most popular entry is procmail, followed by
  deliver.

  Slocal comes with MH. It can be used to process incoming mail based
  on the contents of any of the headers. Actions include filing
  messages, running commands, printing messages on your terminal and
  so on. The configuration is made in ~/.maildelivery. People seem to
  have trouble with slocal bugs, and you can't use it if you don't
  have write permission on your system maildrop so a lot of people
  have opted for the alternatives, but it's easy to use and comes with
  MH.

  procmail is quite popular and has a very powerful configuration
  file. However, the syntax is its own, but it is easy to learn given
  a couple of good examples. Its advantages are its small size and
  speed. Like deliver, procmail may be installed as a delivery agent
  so you would not even have to have a .forward file.

  Deliver can run any script or program (called ~/.deliver), so you
  really can do anything you want to incoming mail. One feature that
  it sports that no other does is that you can install it as a local
  mailer in place of /bin/mail. If it's the local mailer, you don't
  need to have a .forward--~/.deliver is run anyway. In addition, it
  allows the system administrator to write some programs to filter
  everybody's mail. It came with my Linux system, so installation was
  non-existent.

  I started with slocal, and then moved to deliver. I switched to
  procmail because of a bug in deliver (which I think has since been
  fixed) whereby a blank line would be inserted into the header before
  header fields with numbers in them.

  I am still using procmail and probably will do so indefinitely since
  it is powerful, there are many spam filters written in it, and it
  coexists with MH and Gnus so well.

  My recommendation is to use the one that is installed on your system
  or get procmail. Here are the URLs for the filters mentioned in this
  document:

    http://www.procmail.org/

From: "Eric D. Friedman" <friedman at hydra.acs.uci.edu>
Date: 28 Aug 1996 08:28:46 GMT

  See http://www.faqs.org/faqs/mail/filtering-faq/index.html.

From: Stephen R. van den Berg <berg at pool.informatik.rwth-aachen.de>
Date: Mon, 1 Aug 1994 00:00:00 -0800

  Procmail can be used to create mail-servers, mailing lists, sort
  your incoming mail into separate folders/files (real convenient when
  subscribing to one or more mailing lists or for prioritizing your
  mail), preprocess your mail, start any programs upon mail arrival
  (e.g. to generate different chimes on your workstation for different
  types of mail) or selectively forward certain incoming mail
  automatically to someone.

From: Raphael Manfredi <Raphael_Manfredi at pobox.com>
Date: Tue, 28 Jul 1998 13:22:07 +0200

  "mailagent" is yet another mail filter, written in perl, which will
  let you do anything with your mail. It has all the features you may
  expect from a filter: mailing lists sorting, forwarding to MTA or to
  inews, pre-processing of message before saving into folder, vacation
  mode, etc. It was initially written as an Elm-filter replacement,
  but has now enough power to also supplant MMDF's .maildelivery.
  There is also a support for @SH mail hooks, which allows you to
  automatically distribute patches or software via command mails.

  The mailagent was designed to make mail filtering as easy as it can
  be. It is highly configurable and fairly complete. Rules are
  specified in a lex-like style, with the full power of perl's regular
  expressions. The automaton supports the notion of mode, and header
  selection has many magic features built-in, to ease the rule writing
  process.

  The distribution comes with a set of examples, an exhaustive test
  suite, and naturally a detailed manual page. It should be noted that
  the mailagent will work even if your system administrator forbids "|
  programs" hooks in the ~/.forward, provided you have access to some
  sort of cron daemon.

    http://www.cpan.org/authors/Raphael_Manfredi/