Yes, discussions of acks always seem to (de)generate lots of issues of
functionality levels, types of acknowledgements, and so on. A lot of
this was beaten to death in early rounds on ietf-ack, to no obvious
fruitful outcome. I guess what I was hoping is that MIME provides a
framework (parameters on the content-type line) that allows us to
specify which level we're talking about, rather than to argue endlessly
over which level we SHOULD be talking about.
Personally, for example, I believe that MTA-level acks are nearly
completely worthless. The only ack worth anything, to my mind, is an
ack from the end-user, indicating that he has really seen your mail.
Otherwise, you can't ever really know if it got lost downstream of the
ack. But rather than push this strong opinion on the world, I'd be
happier with a framework where the ack-request could say what kind of
ack it is seeking, and the ack itself could declare what kind of ack it
is. Are there any levels that couldn't be handled in the MIME
framework? I think not in theory, but in practice it will be a while
before there are very many MTA's that are prepared to responde to
"Content-type: application/ack-request" buried deep in a multipart MIME
message. This doesn't much worry ME because I don't want MTA-level
acks, but it may be a problem for other folks.. -- Nathaniel