Would the mailing list software replace the Sender: Scott header
field, or would it reject the submission ?
John Levine wrote:
Replace it, since the list is the Sender: for the mail it sends.
This has nothing to do with DKIM, Sender-ID, or anything other than
RFCs 2822 and 822.
Such practice is problematic with DKIM, see below.
RFC 2822 section 3.6.2 describes originator fields. By my reading it
is pretty clear that a list should add a Sender: field with the list's
name since it's the list that's sending the mail.
Dave Crocker wrote:
+1.
A mailing list agent often and reasonably changes a message in substantial
ways. Even if a particular agent does not make changes (other than
re-posting) it is, in fact, re-posting. That makes the mailing list agent
the address that is appropriate for the rfc2822.Sender field.
I'm observing regular cases of originator signature breakage
by mailing lists which DO NOT modify mail body or header in
intrusive ways. This happens every time the poster included
a Sender header field in its original posting, and then sign it.
A mailing list which replaces the original Sender by its own
causes a signature breakage, quite unnecessarily.
Unfortunately the RFC 4871 wants a Sender signed:
The following header fields SHOULD be included in the signature,
if they are present in the message being signed:
o From (REQUIRED in all signatures)
o Sender, Reply-To ...
and RFC 2822 only allows one instance of a Sender header field.
It would be nice to have a clear guideline on what a mailing list
should do with a Sender, and/or a guideline that DKIM should not sign
the Sender field if message is intended for posting.
Mark
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