Proxmox Mail Gateway - Protect mail server against spam, viruses and malware with Proxmox Mail Gateway security for businesses, government, education and non-profit organizations.

SpamAssassin - Use this program to "Unspam" your mailbox(es).

Rspamd - Rspamd is an advanced spam filtering system that allows evaluation of messages by a number of rules...

SpamTitan - Comprehensive Email Protection. 99.99% Spam Detection. Blocks phishing, viruses, malware and other email threats.

MailScanner - MailScanner is a open source email security system design for Linux-based email gateways.

SpamHero - SpamHero is a professional spam filtering accuracy while lowering the cost to domain and business owners.