Eigenpoll : Spam fighting software : Spamish Inquisition (mtaproxy)

http://www.freenet.org.nz/python/mtaproxy/

Spamish Inquisition is an SMTP proxy which uses SpamBayes, and Exim (or your favourite MTA) to intercept spam messages and perform aggressive teergrubing against the spammers' mailservers. (Teergrubing is an offensive practice which hampers spammers' ability to fulfil their quotas and make their money).