Constrictor is a utility developed for the parsing, filtering, and delivering mail as a mail delivery agent; ability to deliver to maildir and Unix mbox format mailboxes, etc.
Pine is an openly developed utility for reading, sending, and managing electronic messages; designed by the Office of Computing & Communications at the University of Washington.
MailScanner is an openly developed utility which serves as an email virus scanner, as well as spam tagger; supporting Postfix, McAfee, eTrust, and other anti-virus scanners.
SPAMato is an openly developed utility which serves as an add-on for Outlook, an extension for Thunderbird and Mozilla Mail, or as a stand-alone application.
