Message-Id: <3.0.32.19971027114630.007a8dd0@pop.dial.pipex.com>
Date: Mon, 27 Oct 1997 13:00:24 +0000
To: Jamie Zawinski <jwz@netscape.com>
From: Graham Klyne <GK@ACM.ORG>
Subject: Re: Can different messages have the same Message-ID
Cc: drums@cs.utk.edu
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"

At 13:05 26/10/97 -0800, Jamie Zawinski wrote:
>Jacob Palme wrote:
>> 
>>    but need not cause a change in the Message-ID. For example,
>>    a receiving mailer can get two copies of the same message with
>>    different values of "To", "Cc" or "Bcc".
>
>Why do you think it's ok to change the recipient list, but keep the
>same ID?  The two messages offer substantively different information
>to the recipients; it's not ok to read one and not the other.
>
>A better way of approaching this might be, "what is the function of the
>Message-ID"? 
>
>I'd answer that as, "two messages are the same message if and only if
>they have the same ID."  Which chases the problem to: "what does `the
>same' mean?"  I think it means, "the two messages contain identical
>information, modulo any routing information that may have been added."

OR: "... are the same if one can be deleted without significant loss of
information to the recipient"?  (This suggests changes to To:, Cc:, etc.
*should* require a new Id?)

Another thought:  doesn't "Content-ID" do for body content?
(But what about Subject:"?).

GK.
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Graham Klyne