SMTP email proxy and relay server
Client daemon to move mail from POP and IMAP to your local computer
Gross greylisting server
JavaScript/XML engine for Apache
one server framework
Open source DMARC implementation
mapSoN is a challenge/response spam filter for Unix
Petidomo is a small, easy-to-administer mailing list server
A Scalable Spam Filtering Architecture
Outgoing email rate limiter
forwards re-encrypted PGP/GPG mail to a group
Blocks spam without blocking any legitimate messages