[exim] Blackhole Email question

Hey there, I have two big domains that have been around for a long time
(10 years each at least) and I just convinced both owners of each of the
domains to turn off their damn catch-alls finally. Now I'm running into
the issue of the machine rejecting a ton of users that no longer "exist".

My question is this, I could put a catch all back and just forward all
the nonsense to a unused account, but I was wondering how do I black
hole an email so it's gone from the server completely?