Just a follow up from this because:
smtp account = notification email = reply email I see the following:
All the bounced replies are going to the rejected queue for forum replies. This is a blessing and a curse. A blessing because I can see the bounce reasons to diagnose email issues. A curse because the rejected queue is supposed to be for rejected attempts at reply.
It also results in a 
user being created:
I prefer if the bounced email list also contains a box to view the bounces. These should be separate from the failed reply by email emails where the bounced emails are now also landing.