SpamAssassin - Use this program to "Unspam" your mailbox(es).
Mailwasher - Over 8 million people use MailWasher as their spam filter
SPAMfighter - SPAMfighter and Microsoft have built the strongest and most effective anti spam filter for Outlook, Windows Live Mail, Outlook Express & Thunderbird
SpamHero - SpamHero is a professional spam filtering accuracy while lowering the cost to domain and business owners.
Spam Reader - Spam Reader is a free anti-spam add-on for Microsoft Outlook.
Bazzacuda - Barracuda Networks is the worldwide leader in Security, Application Delivery and Data Protection Solutions.