Proofpoint - Proofpoint provides cloud-based email security, e-discovery and compliance solutions for companies to protect sensitive business data.
Proxmox Mail Gateway - Protect mail server against spam, viruses and malware with Proxmox Mail Gateway security for businesses, government, education and non-profit organizations.
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.
Rspamd - Rspamd is an advanced spam filtering system that allows evaluation of messages by a number of rules...
dmarcian - Safeguard your email from abuse
SpamAssassin - Use this program to "Unspam" your mailbox(es).