parp is a powerful, extensible e-mail filter with sophisticated anti-spam
capabilities. It's designed as a complete replacement for procmail, is
MIME-aware, and acts as a filter, daemon, or on mailboxes. It uses the Open
Relay Database as part of its spam-detection heuristics, and it has a
DBM-format database of trusted e-mail addresses to ensure that false positives
are kept to a minimum. It can perform duplicate removal by message ID, and has
many other features.
