hMail Server - hMailServer is a free e-mail server for Microsoft Windows.
SpamAssassin - Use this program to "Unspam" your mailbox(es).
Postfix - Postfix is a mail transfer agent (MTA) that routes and delivers electronic mail.
MailScanner - MailScanner is a open source email security system design for Linux-based email gateways.
PowerMTA - PowerMTA is an industrial-strength software for high-volume email delivery.
Rspamd - Rspamd is an advanced spam filtering system that allows evaluation of messages by a number of rules...