I've never used post office or mail marshall, but I always set up a default address for every domain, so typo email addresses do get to somewhere instead of failing.
all failed messages could easily be forwarded to the default address.
the problem is, if you have a fairly busy email server, you will have to have someone going through the inbox for the default address looking for where the failed messages should have gone and seeing if they can be forwarded to the correct place.
labour wise, leave it as it is, let the original sender fix the address.
let the original sender realise they are not using a valid address.
the failed message is the only way a specific email address is removed from the spam list(s) so stopping it is not a good thing on any business server.