Rspamd
An advanced spam filtering system
Rspamd provides spam filtering for both large email services providers and small personal mail servers. Rspamd utilises many techniques to filter spam, such as content filtering, regular expressions, external policies support (such as DKIM, DMARC, ARC and various DNS based lists), statistical methods and advanced machine learning techniques, such as neural networks.
Rspamd core is written in plain C for better performance while the main filtering features are powered by Lua language. There is also Web interface in JavaScript embedded in Rspamd.
Rspamd project has a friendly community and active communication channels.