MailScanner - MailScanner is a open source email security system design for Linux-based email gateways.
Zimbra - Zimbra is trusted by over 500 million users to increase productivity with a complete set of collaboration tools while maintaining total control over security and privacy.
Proxmox Mail Gateway - Protect mail server against spam, viruses and malware with Proxmox Mail Gateway security for businesses, government, education and non-profit organizations.
Roundcube - Web-based IMAP email client
Rspamd - Rspamd is an advanced spam filtering system that allows evaluation of messages by a number of rules...
Microsoft Exchange Server - Microsoft Exchange Server is a messaging and collaborative software product developed by Microsoft.