I'm confused. You said that you foresaw an eventual overhaul of the
message format. If not for the reasons Eric is talking about,
for what reasons?
I don't know what reasons Eric is talking about, so I can't speak about
those.
When I made my earlier statement, I was thinking that it would take
some really signifcant, generally-usable improvements in the service
provided by the mail system in order to justify the pain of
transitioning to a completely new system. Since that time I've
concluded that none of these improvements require significant changes
to the message format. They would however require significant changes
to SMTP (though probably doable within the current extension
mechanism) and significant additional infrastructure.
So now I would say that a significant change to the message format
does not seem to be technically justified by any improvements to
the mail system that I've thought of or seen proposed.
Keith