Subject: [dmarc-ietf] Let's Work on the Reverse Tree Walk Text

From: Todd Herr <[email-masked]>
Date: Wed, 16 Feb 2022 11:02:18 -0500

Greetings.

This is a companion thread to the "Let's Work on the Tree Walk Text" thread
that I started on February 16.

The goal of this thread is to come up with a new revision of section 4.6 of
dmarcbis that better captures current group thinking on what the process
for discovery of the Organizational Domain should be. In dmarcbis-05, that
process involved a reverse tree walk.

Current text follows.

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4.6.
<https://www.ietf.org/archive/id/draft-ietf-dmarc-dmarcbis-05.html#section-4.6>Determining
the Organizational Domain
<https://www.ietf.org/archive/id/draft-ietf-dmarc-dmarcbis-05.html#name-determining-the-organizatio>

For any email message, the Organizational Domain of the RFC5322.From domain
is determined by performing a DNS Tree Walk in the reverse order described
in Section 4.5
<https://www.ietf.org/archive/id/draft-ietf-dmarc-dmarcbis-05.html#dns-tree-walk>.
The target of the search is a valid DMARC record that contains a psd tag
with a value of 'y'. Once such a record has been found, the Organizational
Domain is the target domain that would be queried in the next step in this
reverse tree walk. If the first DMARC record returned does not contain a
psd tag with a value of 'y', that domain is the Organizational Domain. If
the maxmimum depth of the reverse DNS Tree Walk is reached without a DMARC
record being located, the RFC5322.From domain is the Organziational Domain.

For example, given the RFC5322.From domain "a.mail.example.com", a series
of DNS queries for DMARC records would be executed starting with "_dmarc.com"
and potentially finishing with "_dmarc.a.mail.example.com". If the "_
dmarc.com" record contains a psd tag with a value of 'y', then the
Organizational Domain for this RFC5322.From domain would be determined to
be "example.com", the domain of the DMARC query executed after the query
for "_dmarc.com".
<https://www.ietf.org/archive/id/draft-ietf-dmarc-dmarcbis-05.html#section-4.6-2>

Note: If no applicable DMARC policy is discovered for the RFC5322.From
domain during the first tree walk, then there is no need to search for an
Organizational Domain, as the DMARC mechanism does not apply to the message
in question.

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-- 

*Todd Herr * | Technical Director, Standards and Ecosystem
*e:* [email-masked]
*m:* 703.220.4153

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