On Mon 01/Nov/2021 21:35:07 +0100 John R Levine wrote:
On Mon, 1 Nov 2021, Alessandro Vesely wrote:
On Sun 31/Oct/2021 16:01:03 +0100 John Levine wrote:
It appears that Alessandro Vesely <ves...@tana.it> said:
Another criterion, beside tree-walk and PSL, could be to look at the
d= tag of the DKIM signatures that are aligned with the From: domain.
Would that be semantically equivalent to the procedure described in
the current Section 6.7.2? >>>
I don't understand what you're proposing. Are you saying to look for
DMARC records at the d= domains in the signatures on a message? >>
Yes, it might be a valid hint in some cases.
What if it has no signatures but might be SPF aligned?
The existence of an SPF record is less indicative, as the protocol suggests
to publish a record for each host. Yet, in case the SPF identifier is a
parent domain, it might be a valid hint too.
I still don't understand. If a message has no DKIM signatures, and the sender
uses SPF alignment, where do you look for _dmarc records? A concrete example
or two would be helpful.
Today I couldn't find the time to look for messages where the Return-Path: has
a domain that is an ancestor of the From: domain. (Albeit I see not so many
messages, I'll try and fill Scott's request[*] when time permits.)
With DKIM it's more likely to find the org domain. Mail sites that use
subdomains, possibly in order to receive replies at different MXes, can still
publish DKIM keys there. In that case, a receiver can try d= rather then
walking the tree.
For example:
Return-Path: <u...@sales.example.com>
Received: from mail.ny.ext.example.com (mail.ny.ext.example.com [192.0.2.4])
[...]
DKIM-Signature: v=1; d=example.com
[...]
From: Mr. User <u...@sales.example.com>
Subject: Isn't this quite common?
It could happen with SPF too, but I think it's unlikely.
In any case, an aligned identifier would be just a hint. If there's no DMARC
record, the receiver has to walk the tree.
Best
Ale
--
[*] https://mailarchive.ietf.org/arch/msg/dmarc/_Hoj9JrsJrZzPnjnRbsX0zRgOJg
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