Mailwasher - Over 8 million people use MailWasher as their spam filter
SpamHero - SpamHero is a professional spam filtering accuracy while lowering the cost to domain and business owners.
SPAMfighter - SPAMfighter and Microsoft have built the strongest and most effective anti spam filter for Outlook, Windows Live Mail, Outlook Express & Thunderbird
SpamAssassin - Use this program to "Unspam" your mailbox(es).
Spam Reader - Spam Reader is a free anti-spam add-on for Microsoft Outlook.
SpamTitan - Comprehensive Email Protection. 99.99% Spam Detection. Blocks phishing, viruses, malware and other email threats.