SpamAssassin - Use this program to "Unspam" your mailbox(es).
docNCRYPT - docNCRYPT is a cybersecurity platform which only focuses on its core services in protecting your email directly from the different email service provider and allows you to integrate your business email portal in the online service.
MailScanner - MailScanner is a open source email security system design for Linux-based email gateways.
encryptomatic - encryptomatic is a smart email encryption software which provides tons of tools in encryption protocols for secure communication and business transaction.
Rspamd - Rspamd is an advanced spam filtering system that allows evaluation of messages by a number of rules...
Protected Trust - Protected Trust works to enable businesses to experience high productivity and security with Microsoft 365 and Surface.