On 6/24/2020 11:35 AM, Jim Fenton wrote:
On 6/23/20 9:19 PM, Dave Crocker wrote:
On 6/23/2020 4:14 PM, Jim Fenton wrote:
I do have a concern about Sender:. It has existing semantics defined in
RFC 5322 Section 3.6.2, and this proposal might conflict with that
I don't think it conflicts at all. So it will help for you to explain
your concern in detail.
Quoting RFC 5322 Section 3.6.2:
For example, if a secretary were to send a message for
another person, the mailbox of the secretary would appear in the
"Sender:" field and the mailbox of the actual author would appear in
the "From:" field.
and
If the from
field contains more than one mailbox specification in the mailbox-
list, then the sender field, containing the field name "Sender" and a
single mailbox specification, MUST appear in the message.
In the latter example, the From: header field could contain addresses
from different domains, and the Sender: header field would indicate
which of them actually sent the message.
Not 'which of them', but 'who'. The point of the second quoted text is
to mandate a separate Sender:, when the From: contains more than one
address. But it does not specify a different semantic for Sender:
If either message in question goes to a mediator, the Sender address
in the original message would be lost and replaced by the email
address of the mediator, and the original information would be lost.
I'm not sure if that's a significant problem in practice, but pointing
out the possible conflict with currently specified usage.
One can indeed imagine a scenario where it matters, but no, it's not
likely. In any event, the mediator is posting a new message and has a
'right' to retain or modify whatever it wishes.
So if this is the 'conflict' you see, I'll disgree. Rather:
Replacing Sender: is vastly better than modifying From:.
That's the entire motivation for my suggesting DMARC switch to
Sender:.
Please explain why it is important that specifically the Sender:
header field be used for this.
From: is demonstrably problematic. Sender: isn't.
Sender: is a long-standing field, similar to From:, but without it's
history of interesting MUA-level use that DMARC is well-established as
creating problems for.
d/
--
Dave Crocker
Brandenburg InternetWorking
bbiw.net
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