Re: [dmarc-ietf] ARC questions

Michael Thomas <mike@mtcc.com> Mon, 23 November 2020 20:18 UTC

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To: John R Levine <johnl@taugh.com>
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From: Michael Thomas <mike@mtcc.com>
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Date: Mon, 23 Nov 2020 12:18:12 -0800
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Subject: Re: [dmarc-ietf] ARC questions
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On 11/23/20 12:09 PM, John R Levine wrote:
>
>> Since this is an experiment, do we have an idea of what the rest of 
>> the problem is after the typical mailing list-like signature breakers 
>> are excluded?
>
> Sorry, this question makes no sense. The point of ARC is to deal with
> the kind of breakage that mailing lists cause.
>

1) A mailing list creates an auth-res on the incoming mail to the list

2) It modified the message

3) It resigns the message with DKIM

4) It is then delivered to the subscriber's mail server

5) The destination mail server can look at the incoming message 
including the mailing list's auth-res and decide whether to trust it or 
not just like ARC.

It seems to me this covers the vast majority of cases. What are the 
other cases where this is not sufficient and how significant are they in 
reality?

Mike