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

Mailwasher - Over 8 million people use MailWasher as their spam filter

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

SPAMfighter - SPAMfighter and Microsoft have built the strongest and most effective anti spam filter for Outlook, Windows Live Mail, Outlook Express & Thunderbird

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

Spam Reader - Spam Reader is a free anti-spam add-on for Microsoft Outlook.