Procmail (http://procmail.org/) is a powerful Mail Delivery Agent (MDA) capable of sorting and filtering mail based on rulesets called recipes. It's rather *nix-centric, terse, mature, and proven. However, it is now unmaintained.
Procmail is a versatile mail delivery agent (MDA) for Unix-like systems. If features a simple language for articulating delivery rules (aka recipes) to sort, forward, manipulate, and otherwise process incoming email messages.
Procmail was created in the early 1990s by Stephen R. van den Berg. After his involvement waned, Philip Guenther took over as maintainer, and published some new versions at http://procmail.org/. However, this site is now dead, and as of 2010, Guenther recommends users to switch to alternative tools such as maildrop.
In spite of its age and security issues, Procmail remains popular in some environments.
Resources
manpagesprocmail(1) - command options and overviewprocmailrc(5) - configuration file languageprocmailsc(5) - scoring syntax forprocmailrcprocmailex(5) - examples of common or interestingprocmailrcrules and constructs
- procmail.org mirrored at archive.org (last live snapshot, October 2015)
- Nancy McGough's Infinite Ink's Procmail Quick Start (2006)
- Era Eriksson's mini-FAQ and debugging tips (2001)
- Jari Aalto's Procmail tips (2011)
(Copied from Stack Overflow's procmail tag info page.)
