Re: [dmarc-ietf] I-D Action: draft-ietf-dmarc-dmarcbis-03.txt

Alessandro Vesely <> Thu, 19 August 2021 11:18 UTC

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Subject: Re: [dmarc-ietf] I-D Action: draft-ietf-dmarc-dmarcbis-03.txt
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On Wed 18/Aug/2021 22:17:57 +0200 Todd Herr wrote:
> The main update in this draft is removal of the "pct" tag, with an 
> explanation as to why, and an introduction of the "t" tag in an effort 
> to maintain the functionality provided today by "pct=0" and "pct=100".

As held earlier, I disagree with such gratuitous breaking of the 
existing installed base and published records.

It goes without saying that domains who are publishing pct=0 will 
slowly adapt by adding t=y and never removing pct.  Those who publish 
pct=50 and are satisfied with it will have to give up, despite their 
own operational experience.

In any case, I object to the use of the Probability Mass Function as 
applied to Binomial Distributions argument.  It presumes that the 
percentage in question refers to the number of messages sent during a 
given day, which was never specified.  The spec said "Percentage of 
messages from the Domain Owner's *mail stream*".  The random function 
applied to such stream is equivalent to computing a Monte Carlo 
integration on a finite set.  Since *all samples* are eventually 
considered, the result tends to the exact value.