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 minimise the amount of code running as the root user.
