What are some alternatives?
When comparing SpamAssassin and Proxmox Mail Gateway, you can also consider the following products
Scrollout F1 - Scrollout is a free and easy to use anti-spam email gateway designed for Linux & Windows administrators without advanced email security experience.
Mailwasher - Over 8 million people use MailWasher as their spam filter
MailScanner - MailScanner is a open source email security system design for Linux-based email gateways.
Kolab Community - Kolab Groupware is a secure, scalable, reliable, flexible, full-featured collaboration suite.
Altospam - Antispam and antivirus software on Cloud
Barracuda Email Security Gateway - Barracuda's Email Security Gateway is a powerful antivirus filter specifically designed to identify and eliminate email-borne threats, stopping hazards before they reach the network.