🚀 go-pugleaf

IMAP2bis solves the problem by extending IMAP2 to transmit the MIME structure
of messages.  So, for remote mailboxes, you don't need to fetch the entire
text of the message just to get its MIME structure.

This was one of the things that caused a long debate in the MIME working
group, with me having to fight tooth and nail to make sure that MIME didn't do
things that would make the determination of MIME structure difficult (e.g. the
prohibition of recursive encoding is due to my insistance).

I don't think that having a separate structure index in the message itself is
a good idea, because that introduces a new failure mode in which the actual
message structure doesn't correspond to its index.  We're all better off
making sure that it continued to be easy to parse MIME quickly.