and I'm inclined to think that annotations added to a message after
delivery really don't belong in the message header. we want to put
things there because it's easy to do so, not because it makes good
sense.
From a practical point of view, I think this is debatable.
It's certainly possible to create a new MIME type for each envisaged
piece of information, but practically message headers have a privileged
role.
1) They are easy to find without parsing a complex MIME structure.
2) They are often available in cases where the actual body isn't
directly available.
3) They are intended for meta information about the message rather
than message content per se, so it could be argued that they are the
only
correct place to add annotations which describe aspects of the message
rather than new content.
yes, yes, and yes. these are all reasons why it's easy to use message
headers. and MIME types are an even worse place to put such
annotations.
however message headers were originally intended for use by the author
or his user agent. a couple of exceptions were made for MTAs
(Received) and delivery agents (Return-Path). now things have gotten
out of hand, and we have everybody and his brother scribbling on the
message, so much that it's hard for the recipient (or his user agent)
to make sense of it.
what we need IMHO is something akin to an annotation facility in IMAP
and/or POP, that stores the annotations separately from the actual
message.