This would be useful. When creating a "catchall" rule, there are still certain recipients or other conditions that may warrant a 550 NDR being sent back to the original sender. Our only other option is to manually input all our aliases, one by one, which would result in NDRs being sent for inbound emails that don't match a Route rule.
We need the option to create a Route rule that bounces the incoming email back to the original sender, instead of accepting it. What would be even better, is if we could customize the NDR status code as well!
In the same situation as the original poster. +1