fetching, filtering and delivering emails

 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.