Mailagent allows you to process your mail automatically.  Given a set
of lex-like rules, you are able to fill mails to specific folders,
forward messages to a third person, pipe a message to a command or
even post the message to a newsgroup.  It is also possible to process
messages containing some commands.  The mailagent is not usually
invoked manually but is rather called via the filter program, which is
in turn invoked by sendmail.

Most portion of this package is written in Perl and version 5.01M or
higher is known to work nicely.

See the man page for the detailed information.