Mailu - Mailu is a simple yet full-featured mail server as a set of Docker images.
Proxmox Mail Gateway - Protect mail server against spam, viruses and malware with Proxmox Mail Gateway security for businesses, government, education and non-profit organizations.
Microsoft Outlook - Organize your world. Outlook’s email and calendar tools help you communicate, stay on top of what matters, and get things done.
Rspamd - Rspamd is an advanced spam filtering system that allows evaluation of messages by a number of rules...
MailEnable - MailEnable is a Windows based mail server and email server program that is packed with the state of the features and functions like antivirus and spam filtering system, webmail management system, cardDAV, CalDAV and much more.
SpamAssassin - Use this program to "Unspam" your mailbox(es).