SPAMfighter - SPAMfighter and Microsoft have built the strongest and most effective anti spam filter for Outlook, Windows Live Mail, Outlook Express & Thunderbird
dmarcian - Safeguard your email from abuse
Spamihilator - The free Anti-Spam-Filter Spamihilator removes more than 98% of spam mails before they even get into your inbox.
Proofpoint - Proofpoint provides cloud-based email security, e-discovery and compliance solutions for companies to protect sensitive business data.
Mailwasher - Over 8 million people use MailWasher as their spam filter
Barracuda Email Protection - Barracuda Essentials offers advanced Office 365 security features including email scanning, archiving, backup & recovery, and real-time phishing defense.