I have a rather convoluted multi-instance setup that mostly works to my liking, with spam-filters, hand-off to mailman, dkim-signing and whatnot. One problem is that mis-typed outgoing addresses (host part) from my local, authenticated users end up deferred (450) and not bounced back to the sender. I am a bit wary of enabling bounces, but if I can make sure that I don't bounce incoming mail, I should be OK.
Long story short, If in a specific postfix instance I am SURE I'm only handling mail submitted by authenticated users, I should be OK to change unknown_address_reject_code to 550 ? I don't want to do the change in submit (before queue) because I have a dance with DKIM signing before handing off to address-mapping and further to relay/local delivery/mailman,
