If this message returns (again, the
body being accepted in provisional mode) before the problem
is dealt with (alteration of recipient's magic phrase timestamp,
appearance of a sender payment account) they get their connection
dropped on presentation of an already-seen message-ID.
Hmm. I think I'd be inclined to wait a minimum amount of time
between the "first seen" and "reject message" phases. Give people a
little while to get their updated information out there, before you
outright reject the message.