MailScanner - MailScanner is a open source email security system design for Linux-based email gateways.
SpamTitan - Comprehensive Email Protection. 99.99% Spam Detection. Blocks phishing, viruses, malware and other email threats.
Proxmox Mail Gateway - Protect mail server against spam, viruses and malware with Proxmox Mail Gateway security for businesses, government, education and non-profit organizations.
MailCleaner - Cloud & on-premise anti spam software for businesses
Rspamd - Rspamd is an advanced spam filtering system that allows evaluation of messages by a number of rules...
Vade Secure - Email security to protect against email-borne phishing, spear phishing, malware, and ransomware. Email security and management based on artificial intelligence.