Couldn’t find anything newer referencing this issue.
Having the same problem. Came across a PR on github that for some reason never got implemented. Testing it here on the 2025-12a build successfully (with caveats).
mailcow/mailcow-dockerized6773
There’s 2 files that get revised with some additional code, then either restart the whole thing or rspamd and nginx (I think). I just restarted it all.
The caveat is this. While rejected messages do end up in quarantine, since no mailboxes are defined, who does the quarantine notification go to?
IMO they should go to the intended recipient, or catchall (if defined) on the relay target. This is behavior when mailcow IS NOT a relay.
Perhaps thats why the PR hasn’t been accepted yet?
I don’t know if the author of that PR will make the added changes, but at least this allows the message to be retained for later review by the admin.