@paco To me, the main advantage of operating my own #email system is that I'm free to configure my inbound #MX so that it outright rejects "crap" (containing #malware or hitting a certain #spam score). With abusive mail, there's no way to reject anything once it was accepted, as this would mean #bounces, and therefore #backscatter.

BTW, you can allow your users to do a lot of interesting filtering stuff using #sieve (and manage-sieve). But probably not what you described here. 😞

I think I managed to get rid of most (all?) #backscatter on the LURK server that handles the mailing lists.

Posting the #postfix tweaks here in case this is useful for someone else. Feedback welcome!

https://things.bleu255.com/runyourown/Backscatter_Rejection