maildrop is a replacement for your local mail delivery agent,
similar to mail/procmail.
- maildrop reads a mail message from standard input,
  then delivers the message to your mailbox.
- maildrop will optionally read instructions from a file,
  which describes how to filter incoming mail.
  Instructions can be provided having mail delivered to
  alternate mailboxes, or forwarded somewhere else.
  Unlike procmail, maildrop uses a structured filtering language.
- maildrop knows how to deliver mail to mbox-style mailboxes and maildirs.
- maildrop is written in C++, and handles resources more efficiently.

maildrop can be used with sendmail, qmail, and other MTAs.

WWW: http://www.courier-mta.org/maildrop/