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

Alessandro Vesely <vesely@tana.it> Sat, 31 July 2021 09:40 UTC

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From: Alessandro Vesely <vesely@tana.it>
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Subject: Re: [dmarc-ietf] Some Proposed Language for a New pct Tag Defintion
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On Fri 30/Jul/2021 22:06:39 +0200 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:


I still dislike this limitation.  I previously showed that users seem to change 
pct= with some salt.  In addition, how should implementations amend their code? 
  What shall a receiver do if it finds intermediate values of pct?

I'd keep allowing intermediate values.  Substitute /Possible values are as 
follows:/ with /RECOMMENDED values are as follows:/.

For case 0:

YOUR TEXT:
      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.

MY PROPOSED ALTERNATIVE:
      0:  A request that messages producing a DMARC "fail" result never
          have the specified policy applied.  The special meaning of
          this value is to have mailing lists which discriminate message
          handling by author's domain policy apply From: munging
          (see [Section X.Y.Z]) while final receivers still apply no
          policy.


Best
Ale
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