rspamd is used nowadays. Add sieve filtering to automatically move mails with a 7.0 or higher to a spam-folder. Manually move mails there that haven’t been detected and move mails out of the spam folder that have been falsely detected (personally don’t have any false positives with rspamd).
Then set up bayes learning with rspamd, either when mails are moved between folders or every few hours.










I just googled something. Don’t remember what I ended up on. Probably some blog post combined with rspamd’s website. It depends on your mailserver anyways.