SpamAssassin - Use this program to "Unspam" your mailbox(es).
Rspamd - Rspamd is an advanced spam filtering system that allows evaluation of messages by a number of rules...
SPAMfighter - SPAMfighter and Microsoft have built the strongest and most effective anti spam filter for Outlook, Windows Live Mail, Outlook Express & Thunderbird
Oikik Antispam - Oikik is a cloud-based email filtering service that works with your existing email service.
SpamHero - SpamHero is a professional spam filtering accuracy while lowering the cost to domain and business owners.
Proxmox Mail Gateway - Protect mail server against spam, viruses and malware with Proxmox Mail Gateway security for businesses, government, education and non-profit organizations.