Re: [dmarc-ietf] Some Proposed Language for a New pct Tag Defintion

Barry Leiba <barryleiba@computer.org> Tue, 03 August 2021 12:22 UTC

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From: Barry Leiba <barryleiba@computer.org>
Date: Tue, 3 Aug 2021 08:21:47 -0400
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To: Todd Herr <todd.herr=40valimail.com@dmarc.ietf.org>
Cc: IETF DMARC WG <dmarc@ietf.org>
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Subject: Re: [dmarc-ietf] Some Proposed Language for a New pct Tag Defintion
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The problem I have with leaving pct=0 in as the only (non-default) value is
that it locks history into the protocol.  It makes no sense to have a
binary situation specified by a tag called “pct” that is either 0 or 100.

If we’re leaving this in as a binary thing, (1) we’re already incompatible
with deployments that do pct=20 or whatever, so (2) we might better make it
a y/n or t/f valued tag for that function, deprecate pct entirely, and
leave text in a backward-compatibility section explaining what happened.

I just think that the pct= 0 or 100 thing won’t wear well and will appear
tattered quickly.

Barry

On Tue, Aug 3, 2021 at 8:08 AM Todd Herr <todd.herr=
40valimail.com@dmarc.ietf.org> wrote:

> On Mon, Aug 2, 2021 at 10:10 PM John Levine <johnl@taugh.com> wrote:
>
>> It appears that Todd Herr  <todd.herr@valimail.com> said:
>> >> I like simple, but I also like the idea of a separate section that
>> >discusses the history of the pct tag and why the old values won't work
>> any
>> >longer.
>>
>> OK except:
>>
>> >   remains the default, and "0".  The value of "0" took on unintended
>> >   significance during the experimental stage as a value used by some
>> >   intermediaries and mailbox providers as an indicator to either
>> >   deviate from standard handling of the message and/or to alter the
>> >   substance of reports generated, ...
>>
>> Alter the reports?  Huh?  I was under the impression that the policy
>> didn't
>> affect the reports, much less the pct.
>>
>>
> My apologies...
>
> My memory of the effect of the policy "p=quarantine; pct=0" vis-a-vis how
> Google handles a domain's mail was faulty. I remember when working to
> implement DMARC at $JOB[-1] for our corporate domain, I was seeing data in
> the agg reports from Google when we were at p=none that led me to ask "WTF
> are those hosts?" and digging around the various corners of the internet
> unearthed the unknown at the time to me fix of "Yeah, you gotta be at
> p=quarantine; pct=0" to get reports from Google that make sense.
>
> There are several years old threads on mailop that speak to this topic,
> with outsiders asserting that what is in fact happening is Google Groups is
> rewriting the From when it's p=quarantine; pct=0, and Brandon Long from
> Google in the thread doesn't challenge that assertion, so I'll remove
> reference to the reporting alteration.
>
> --
>
> *Todd Herr* | Technical Director, Standards and Ecosystem
> *e:* todd.herr@valimail.com
> *m:* 703.220.4153
>
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