Re: [dmarc-ietf] A policy for direct mail flows only, was ARC questions

Michael Thomas <mike@mtcc.com> Wed, 25 November 2020 20:37 UTC

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From: Michael Thomas <mike@mtcc.com>
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Date: Wed, 25 Nov 2020 12:37:35 -0800
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Subject: Re: [dmarc-ietf] A policy for direct mail flows only, was ARC questions
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On 11/25/20 12:31 PM, John Levine wrote:
> In article <b0f72407-81ce-9990-4a5b-7b0e5b76e3d7@mtcc.com>om>,
> Michael Thomas  <mike@mtcc.com> wrote:
>> When I was at Cisco, with l= and some subject line heuristics I could
>> get probably like 90+% verification rate across the entire company, a
>> company that uses external mailing lists a lot. Definitely not 100% though.
> I think you will find that at very large mail systems like gmail and
> Microsoft and Yahoo, 90% might as well be 0%. The volume of errors is
> just too high and the number of complaints would be impossible.
>
> While I almost never see the sort of spam leakage through mailing lists
> that Brandon reports, I believe him when he says it's enough of a problem
> that Gmail can't just whitelist traffic from mailing lists.
>

Not everything is service provider. We were investigating this from an 
enterprise standpoint.

And if you can't trust mailing traffic from providers what is the point 
of ARC?

Mike