Mimecast Gateway - Mimecast Gateway is a SaaS-based email security solution that uses sophisticated, multi-layered detection engines and intelligence to protect email data and employees from malware, spam, advanced threats and zero-day attacks.
SpamHero - SpamHero is a professional spam filtering accuracy while lowering the cost to domain and business owners.
dmarcian - Safeguard your email from abuse
SpamAssassin - Use this program to "Unspam" your mailbox(es).
Hornetsecurity - Hornetsecurity offers you comprehensive, integrated managed e-mail security services.
SpamTitan - Comprehensive Email Protection. 99.99% Spam Detection. Blocks phishing, viruses, malware and other email threats.