https://rspamd.com/
Rspamd offers enterprise-grade email security, built on the powerful open-source spam filtering system with advanced features and dedicated support.
open source emailrspamdsecurity
https://poolp.org/posts/2019-09-14/setting-up-a-mail-server-with-opensmtpd-dovecot-and-rspamd/
Sep 14, 2019 - TL;DR: - NO TL;DR: this time, I spent hours writing, you should spend minutes reading. - OK... I explain in WAY TOO MUCH details how to setup a mail server...
mail serversettingopensmtpddovecotrspamd