SpamHero - SpamHero is a professional spam filtering accuracy while lowering the cost to domain and business owners.

Mimecast Secure Email Gateway - Prevent targeted email-borne attacks with Mimecast Secure Email Gateway for cloud-based anti-virus and anti-spam protection.

Proxmox Mail Gateway - Protect mail server against spam, viruses and malware with Proxmox Mail Gateway security for businesses, government, education and non-profit organizations.

FortiMail - Fortinet Email security is designed to block ransomware, phishing, and other cyber threats seeking entry via incoming email and outgoing messages don’t improperly leak sensitive data.

SpamTitan - Comprehensive Email Protection. 99.99% Spam Detection. Blocks phishing, viruses, malware and other email threats.

SpamAssassin - Use this program to "Unspam" your mailbox(es).