How do I reject incoming mails to certain adresses?

I’m using MIAB with some domains set as catch-all aliases, because MIAB isn’t really made for user configurable alias lists. The setup itself works perfectly well for single-users and small groups. There’s one thing I’m unhappy with, though. I can’t reject certain receipients.

While I can add aliases to redirect “bad receipient addresses” into a dedicated inbox that just deletes all incoming mail, I want it actually rejected like it would if there was no user with that address.

Is there any possibility to directly set those receipients somewhere in a configuration file, just like you can exclude certain addresses from greylisting new mails? Any help would be appreciated. And yes, that’s an unsupported modification that is out of MIAB’s scope.

Edit: I’ve done some searching and successfully tried this solution, but I think I need to keep checking /etc/postfix/ after each MIAB upgrade?