[Mailman-Users] Message-ID required - was: Reply-to options not working

Stephen J. Turnbull turnbull.stephen.fw at u.tsukuba.ac.jp
Tue Feb 6 05:09:42 EST 2018

Dimitri Maziuk writes:

 > Heh. I personally believe that a message sent by a mailing list
 > *must* have the mailing list as the originator: dkim, id, and
 > whatever else.

First, please be careful with terminology.  *Originator* is
well-defined (RFC 5598) as the agent of the Author that first injects
the message into the mail system.  When mailing lists distribute posts
to subscribers, they function as *Mediators* (RFC 5598).

Even if used loosely, I see no reason here to think of mailing lists
as "originators".  DKIM explicitly provides that multiple signatures
may be present, whether from the same host or different hosts.  For
message identification, Mediators are encouraged to use
Resent-Message-ID and other Resent-* fields to provide trace
information in addition to the MTA's Received fields.  Such features
are available to any agent in the mail system, not restricted to
Authors and Originators.

 > And even if "Message-ID MUST be present and MUST be unique", that
 > doesn't make the converse true: that two copies of the same message
 > *must* carry the same Message-ID.

I don't understand your point.  The RFCs make clear that in the case
of certain trivial modifications (adding trace fields to the header,
for example), the Message-ID SHOULD be preserved.  Further, Mark has
described when Mailman will alter the Message-ID, and I described some
of the cases where people disagree about whether to alter it.

However, for stock Mailman, I think that pretty much everybody who
cares about Message-ID agrees that given the kinds of changes Mailman
makes to messages, it should only change Message-ID in an overriding
case such as preserving privacy on a list that purports to anonymize
posts, or where it interferes with interoperability.  Otherwise you
interfere with features such as local duplicate suppression,
threading, and archiving that depend on stability of Message-ID.

Do you have something to add to that, or disagree with that?


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