BitNotice
I'm currently testing new setups for some of my servers, including ones for spam protection. Rspamd, a spam filter written in C with LUA modules, seems pretty solid. In addition to a large list of header and content filters for scoring, it also handles the usual things like SPF, DKIM, DCC, and RBLs. Complemented by a self-learning Bayesian filter, this should keep out the "junk." The whole thing is complemented by a web interface that provides statistics and allows parameter settings.
Together with Postfix and RMilter, a setup can be created that performs the check as soon as it's received. This allows the email to be rejected immediately, preventing third parties from being bothered by unwanted backscatter.
Here's a brief and somewhat haphazard overview of the Rspamd installation with accessories and its integration with Postfix.
https://rspamd.com/
https://de.wikipedia.org/wiki/Backsca...)
EDIT: Depending on the setup, the postfix user may need to be added to the rmilter group.