I wasn't aware of the problem of guessing which are the correct Resent-* field, tthis does not seem to be that easy, however taking only the first one should be a good heuristic for next release.

I think we now agree on the "automatic processing" part, this only for the receipt part and section 3.6.6 mostly means that From, To, ... fields schould be considered (not the Resent-* fields) while sending an answer for example. For our case it schould be ok to use them as long as ther is no ambiguity (only one Resent-* block).

I'm ok for modifying my patch to reflect our discussion. You'll heard some news from it very soon. I'll also add the patch for not mutating the original message.

After 3.2.1, I'll work on implementing the few api change you discuss this will make the code very usable.