Mailutils is a Swiss Army knife of electronic mail handling.  It offers
rich, strictly RFC-compliant set of utilities, daemons, and filters for
processing the e-mail.

All Mailutils programs are able to operate on mailboxes of any existing
format, ranging from standard Unix maildrops, through maildir and up to
remote mailboxes, which are transparently accessed using IMAP4, POP3,
and SMTP.