Description:

fdm is a program to fetch mail and deliver it in various ways depending on a
user-supplied ruleset. Mail may be fetched from stdin, IMAP or POP3 servers,
or from local maildirs, and filtered based on whether it matches a regexp,
its size or age, or the output of a shell command. It can be rewritten by an
external process, dropped, left on the server or delivered into maildirs,
mboxes, to a file or pipe, or any combination.

fdm is designed to be lightweight but powerful, with a compact but clear
configuration syntax. It is primarily designed for single-user uses but may
also be configured to deliver mail in a multi-user setup. In this case, it
uses privilege separation to minimize the amount of code running as root.