Re: No apologies if you receive this multiple times

At 12.33 -0400 0-05-02, Keith Moore wrote:
> mail delivery systems should probably not try to eliminate duplicates
> on behalf of their users. sometimes you actually want to know that
> you got a copy of the message that was sent through a list even if
> you already received a copy by other means.  so the user agent would
> need to do the duplicate suppression if it is to be done at all.
>
> I don't think we need to find a technical solution to every
> social problem that exists with email.  the problem exists in other
> fields as well - people sometimes get more than one copy of the
> same mail-order catalog, for instance - and we don't lose too much
> sleep over it.

I have many times complained that so few mailers utilize
the opportunities provided by Message-ID, In-Reply-To,
References and (not yet standard) Supersedes to correlate
related messages. Such correlation functions will provide
simple user commands for actions such as "find the message
which this message is a reply to", "find all replies to
this message", "find all message in this thread".

Duplicate messages can be detected either by Message-ID
or by some kind content checksum. Instead of rejecting
one of them (like Usenet News servers do) they should
be correlated.

(If a Usenet News server gets a message with Message-ID
xyz to newsgroup A, and then gets the same message again
to newsgroup B, it will reject the second copy of the
same message, instead of delivering it to newsgroup B.
I can understand why it works like that, but it is not
nice and proper. If two mailing lists gateway to two
newsgroups, then this means that messages sent to both
mailing lists will only occur on one of the newsgroups.)

Example of you can correlate messages with the same Message-ID:

You get a message with
    To: marys@foo.bar.net
    Message-ID: xyz@foo.net.bar

And another message with identical content, and the headers
    To: lizaq@foo.bar.net
    Message-ID: xyz@foo.net.bar

You can then display this to the user something like this:
    To: marys@foo.bar.net
    To: lizaq@foo.bar.net
    Message-ID: xyz@foo.net.bar

If two messages have the same Message-ID but not identical
content, it is still useful to correlate them, for example
    From: marys@foo.bar.net
    To: lizaq@foo.bar.net
    Other messages with the same Message-ID

The recipient can then click on this link to see the other
messages with the same ID.

See also http://dsv.su.se/jpalme/ietf/message-threading.html
-- 
Jacob Palme <jpalme@dsv.su.se> (Stockholm University and KTH)
for more info see URL: http://www.dsv.su.se/jpalme/