heh. But think, those bounces might be telling you about
delivery failures following "broken" forwarding :-)
Most are adverts from broken anti-virus filters.
If I send email and someone does not respond I either ignore or
I follow up with a phone call.
I think we also need a completeness indicator, so you can
say 'this is the complete set of my outgoing MTAs or
these are member of the set of my outgoing MTAs'.
OK, I'll bite. What's the advantage in listing only a proper subset?
If there is an authorization mechanism in place at the receiver
end you can still take the benefit of accreditation even though
you might not be able guarantee that you were able to list out
every one of your legitimate edge email servers.