On Mon, 12 May 1997 01:35:07 +0200, you said:
Does anyone know of a discussion on a retraction function for mail
analogous to an NNTP cancel message? I have looked through the IMC and IETF
sites without success. I saw the draft SMTP extension that allows
supersession and expiration, but that's not quite what I'm looking for. I'd
like to see a way for the sender to cancel a message before it is read by
the recipient.
If there isn't such a proposal on the table is this the place to discuss it?
Yes, this would be the place to discuss it.
No, there's no such proposal as far as I am aware.
There are a number of severe problems you need to deal with in any such
proposal:
1) What level of "guarantee" will the service provide? If the service
*says* it was cancelled, how cancelled is it *really*? (Remember that
Oliver North got strung up because of system backups that contained
e-mail memos he thought were deleted). Is the file *really* erased to
(say) mil-spec standards (overwritten multiple times with random
patterns, and so on), or is it just logically erased, and still
scavengable off the disk, or is it still in a file, and just marked as
"purged"?
2) What if the recipient gets his "You have new mail" bleep right
away, and goes and reads his mail? You then have to deal with (a) the
mail was already read - NOW what do you do? and even worse (b) the
recipient is in the process of reading it when cancelling is
attempted...
3) Many people (myself included) do a lot of programmatic processing
of mail (filtering, filing based on origin/subject, etc) when the mail
is received. There's *NO* way that you will be able to get at a
message to cancel it in this case. Even if the message itself were
removable, there may be other state information that will get
changed. For instance, my 'procmail' filter keeps statistical
information on the number of messages received of different types - if
I receive a message in "Category 3A" that's subsequently cancelled,
how does that change the 'received count' for 3A?
4) Security implications - what level of authentication is needed to
cancel a mailgram? Note that this is a serious issue for the folks
who are doing EDI over e-mail - they most certainly do *NOT* want
people to be able to cancel an EDI-submitted order that easily,
outside the EDI scheme.
5) Implications for e-mail based automatons (Listservs, file servers,
and the like) - what happens if you send in a 'cancel' for a
subscription request? Especially if the Listserv processed it
already? (This is *not* a moot point - I've seen our Listserv receive
a subscribe, process it, and get the "you have been subscribed"
message out all within 2 seconds).
I could probably think of more issues if I hadn't just arrived at the
office and not ingested my usual requirement of caffeine yet. ;)
--
Valdis Kletnieks
Computer Systems Senior Engineer
Virginia Tech
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