Client daemon to move mail from POP and IMAP to your local computer
mailbox synchronizer
Fast Bayesian spam filter along lines suggested by Paul Graham
SOGo Zero-Effort-Groupware
Universal server
Remote anti spam utility
C library for sending e-mail (with attachments) from C/C++
Gross greylisting server
Email reader for RISC OS operating system.
Anti Spam SMTP Gateway
an easy to use pop3 client library in C
one server framework