Currently Domino includes a copy of attachments on delivery failure reports. This should be a configuration option to keep from overwhelming the router or the sender when multiple recipients get failures.
Power users know to go and periodically clean-up the Recent Contacts view. To save everyone some time, when you receive a DFR and resend with a new address, receive a prompt to have the old address (now stored in Recent Contacts) get replaced with the one you just typed.
Attachments should be automatically deleted from delivery failure notifications. As it is now, the attachment is in the Sent message & another copy is in the delivery failure notification. This is obviously inefficient & causes quota issues for those with mail quotas.