Re: [dmarc-ietf] Nonexistent Domain Policy was: Re: Working GroupLast Call: draft-ietf-dmarc-psd

Scott Kitterman <sklist@kitterman.com> Mon, 22 July 2019 10:44 UTC

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Date: Mon, 22 Jul 2019 10:43:47 +0000
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To: dmarc@ietf.org
From: Scott Kitterman <sklist@kitterman.com>
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Subject: Re: [dmarc-ietf] Nonexistent Domain Policy was: Re: Working GroupLast Call: draft-ietf-dmarc-psd
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On July 22, 2019 4:31:40 AM UTC, "Douglas E. Foster" <fosterd@bayviewphysicians.com>; wrote:
>About this paragraph:
>  
>>> The original pre-standardization version of this protocol included a
>  >> mandatory check of this nature. It was ultimately removed, as the
>>> method's error rate was too high without substantial manual tuning
>>> and heuristic work. There are indeed use cases this work needs to
>>> address where such a method would return a negative result about a
>>> domain for which reporting is desired, such as a registered domain
>>> name that never sends legitimate mail and thus has none of these
>>> records present in the DNS.
>  
>This section seems to give a free pass to senders who use non-existent 
>domains, as if such behavior had no impact on the risk posture of the 
>recipient. 
>It seems to say, "You can keep doing this, because so is everyone
>else."
>  
> I would think better language would be along the following lines:
>
>  
>
>"Senders SHOULD register all domains in DNS, as MTA operators MAY block
>
>messages that appear to come from non-existent domains.
>Developers of MTA filtering software SHOULD provide MTA operators with
>the 
>ability to block non-existent domains.
> If such ability is provided, the MTA filtering system MUST provide a 
>mechanism for overriding the filter rule for messages that are
>acceptable 
>to the recipient organization."
>  
>In short, the evaluation of whether manual tuning is worthwhile should
>be 
>left to the discretion of the MTA operator, based on his organization's
>risk tolerance and message characteristics.

I think that it is well outside the scope of this document to impose such a requirement.

Scott K