Depending on the feature, I might agree with that, but I wasn't involved in that decision.

If email only supports something structured with proper MIME headers and multifile is more general (which I *think* is the case, but I haven't actually tried to run any tests to confirm it), does that mean we should have kept multifile in py3?  I'm inclined to say no.  Should we make email support the more general case?  I'll at least keep it in the back of my mind as I/we work on email6.

Multifile is still there in 2.7, at the moment.

I presume you have a use case for the multifile module.  Could you do me a favor and add that use case the set of use cases in the email wiki?
(http://wiki.python.org/moin/Email%20SIG/UseCases).  It would be a good idea to mention there that email is supposed to supersede multifile.