On 4/12/2014 8:04 AM, David Woodhouse wrote:
On Sat, 2014-04-12 at 07:47 -0700, Dave Crocker wrote:
On 4/12/2014 3:49 AM, David Woodhouse wrote:
On Sat, 2014-04-12 at 12:30 +0200, Tom Hendrikx wrote:
Also, I can see good reasoning in the simple concept: when I received
an e-mail from a private person and simply hit reply, I reply to the
person. When I received an e-mail from a discussion-list and simply
hit reply, I expect the reply to go to the discussion-list.
The message came *via* the list. Not *from* it.
Therein likes the problem. The list took delivery of a message from the
author and then re-posted. A mailing list is not a mail relay. It
legally can make any change it wants to the message, because formally it
is posting a new message.
So it SHOULD have a new Message-ID: header, right?
That's one of the points of debate. Again, there are reasonable
arguments for an against.
RFC 5598 extensively considers the question of changing the Message-ID:
3.4.1. Message-ID
When a message is revised in any way, the decision whether to assign
a new Message-ID: requires a subjective assessment to determine
whether the editorial content has been changed enough to constitute a
new message. [RFC5322] states that "a message identifier pertains to
exactly one version of a particular message; subsequent revisions to
the message each receive new message identifiers." Yet experience
suggests that some flexibility is needed. An impossible test is
whether the Recipient will consider the new message to be equivalent
to the old one. For most components of Internet Mail, there is no
way to predict a specific Recipient's preferences on this matter.
Both creating and failing to create a new Message-ID: have their
downsides.
Here are some guidelines and examples:
o If a message is changed only in form, such as character encoding,
it is still the same message.
o If a message has minor additions to the content, such as a Mailing
List tag at the beginning of the RFC5322.Subject header field, or
some Mailing List administrative information added to the end of
the primary body part text, it is probably the same message.
o If a message has viruses deleted from it, it is probably the same
message.
o If a message has offensive words deleted from it, some Recipients
will consider it the same message, but some will not.
o If a message is translated into a different language, some
Recipients will consider it the same message, but some will not.
o If a message is included in a digest of messages, the digest
constitutes a new message.
o If a message is forwarded by a Recipient, what is forwarded is a
new message.
o If a message is "redirected", such as using IMF "Resent-*" header
fields, some Recipients will consider it the same message, but
some will not.
The absence of both objective, precise criteria for regenerating a
Message-ID: and strong protection associated with the string means
that the presence of an ID can permit an assessment that is
marginally better than a heuristic, but the ID certainly has no value
on its own for strict formal reference or comparison. For that
reason, the Message-ID: is not intended to be used for any function
that has security implications.
--
Dave Crocker
Brandenburg InternetWorking
bbiw.net
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