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.
ISOS is an e-mail and web server. It is designed for ease of use and provides a quick way to e-presence for small businesses and organizations who lack the experience to benefit from high performance, open source software such as Sendmail, Courier Mail,