Barracuda Email Security Gateway - Barracuda's Email Security Gateway is a powerful antivirus filter specifically designed to identify and eliminate email-borne threats, stopping hazards before they reach the network.
Mailwasher - Over 8 million people use MailWasher as their spam filter
Symantec Email Security.cloud - Symantec Email Security.cloud provides always-on, inbound and outbound email security against malware, targeted attacks, and advanced threats
SPAMfighter - SPAMfighter and Microsoft have built the strongest and most effective anti spam filter for Outlook, Windows Live Mail, Outlook Express & Thunderbird
Proofpoint Email Security and Protection - Learn about Proofpoint's email security solutions that protect organizations against threats such as email fraud, phishing, spam, bulk email, and viruses.
Spam Reader - Spam Reader is a free anti-spam add-on for Microsoft Outlook.