Website: https://rspamd.com/
Source Code: https://github.com/rspamd/rspamd
Donate: https://opencollective.com/rspamd_project
ΒΆ Description
"Rspamd is an advanced spam filtering system and email processing framework that allows evaluation of messages by a number of rules including regular expressions, statistical analysis and custom services such as URL black lists. Each message is analysed by Rspamd and given a verdict that might be used by MTA for further processing (e.g. to reject a message, or add a special header indicating spam) along with other information, such as possible DKIM signature or modifications suggested for a message."