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

Дилян Палаузов <dilyan.palauzov@aegee.org> Sat, 31 July 2021 09:55 UTC

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To: Todd Herr <todd.herr=40valimail.com@dmarc.ietf.org>, IETF DMARC WG <dmarc@ietf.org>
Date: Sat, 31 Jul 2021 12:55:25 +0300
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Subject: Re: [dmarc-ietf] Some Proposed Language for a New pct Tag Defintion
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Hello,

for me this wording of pct=0 is not clear enough, why the value is
necessary.  Why the value is necessary can be explained by:

When seeing pct=0 mail intermediaries should munge the From: header. 
This allows mail operators to detect problems with DMARC deployment,
before strict DMARC policy is applied.

Greetings
  Дилян

On Fri, 2021-07-30 at 16:06 -0400, Todd Herr wrote:
> Following on to the recent discussion about the pct tag, and
> specifically the disallowing of any values other than 0 and 100, I
> propose the following text and look forward to your comments:
> 
>    pct:  (plain-text integer; OPTIONAL; default is 100).  For the
>       RFC5322.From domain to which the DMARC record applies, the
> "pct"
>       tag is the percentage of messages producing a DMARC result of
>       "fail" to which the Domain Owner wishes its preferred handling
>       policy be applied.  However, this MUST NOT be applied to the
>       DMARC-generated reports, all of which must be sent and received
>       unhindered.  Possible values are as follows:
> 
>       0:  A request that zero percent of messages producing a DMARC
>          "fail" result have the specified policy applied.  While this
> is
>          seemingly a non-sensical request, this value has been given
>          special meaning by some mailbox providers and intermediaries
>          when combined with "p=" values other than "none".  In those
>          cases, in can result in changes to message handling, and/or
>          DMARC reporting for the domain publishing such a policy.  In
>          some instances of altered reporting, it is possible that the
>          altered reports may reveal intermediaries whose handling of
> the
>          domain owners' mail could cause it to produce a DMARC result
> of
>          "fail" when it reaches its final destination.
> 
>       100:  The default, in which a request is made that every
> message
>          that produces a DMARC "fail" result will be subject to
>          application of the specified policy.
> 
> I'll check on this thread on Monday to see where things stand...
> 
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