At 10:01 AM 8/18/94, Dana S Emery wrote:
Privacy needs to be a concern here, unless this feature were
backed up by some form of authentication I would hesitate to
consider it a _good thing_, even assuming it had widespread
implementation. I would not want to see the enablement of
a way for hackers to conduct "mail-wars".
I agree.
But let's postulate that both the message and the cancellation are signed
with PEM or PGP or something, and both signatures match. Under what
circumstances would it be appropriate for an MTA or MUA to make use of the
Obsoletes: header? What feedback (if any) should go to the sender or
recipient?
I can think of several states for a message:
- in transit
- in user's "maildrop", unseen by user
- under control of user's MUA, unseen by user
- seen by user
(These state are by no means exhaustive or even well-defined for many
mailsystems; but they might at least serve as a starting point.)
It's easy (I think) to see that it's perfectly fine to cancel something in
transit, and have the recipient be none the wiser. It's also easy to see
that you don't snatch a message away while a user is reading it, and
pretend that it never existed. But what about between those extremes?
--
Steve Dorner, Qualcomm Incorporated