TMDA is an open source anti-spam system and local mail delivery agent written in 100% pure Python. TMDA combines whitelists, blacklists, a challenge/response system, and special-purpose e-mail addresses called "tagged addresses" to thwart spam.
A python wrapper for Local Delivery Agents (for example, maildrop), which allows an unlimited number of extensions on a mail account with dot-qmail-like functionality.