I don't think Greg -- or any of us -- thinks that IMPP won't support MIME.
We just have a lot of weasel words in the requirements so that we don't
actually *have* to support MIME. I think there is a very high likelihood
that any proposed protocol will carry MIME objects, but there was a
widespread sense that it was not justifiable to actually *require* that the
protocol carry MIME.
> Have you nailed a maximum message size yet?
No. My guess is that such an architectural maximum is likely to be
unimportant in practice compared to the question of providing "instant
delivery." That is, even if we had a message format that allowed terabyte
messages, any current implementation would likely refuse such a large
message as impossible to handle in a suitably timely fashion. The corollary
is that we should avoid defining an architectural maximum based on today's
technology, since future technology changes could enable styles of instant
messaging that are unimplementable now. So I would hope that we define a
message format that allows very large messages, but also define a mechanism
for a given implementation to indicate its own limits on size of messages
carried.
--Mark