On 6/18/20 2:29 PM, Dave Crocker wrote:
> On 6/18/2020 2:10 PM, Jim Fenton wrote:
>> On 6/17/20 12:11 PM, Pete Resnick wrote:
>>> On 17 Jun 2020, at 13:27, Dave Crocker wrote:
>>>> DMARC has nothing to do with display of author information to a
>>>> recipient, and everything to do with differential handling by a
>>>> receiving filtering engine. Were the Sender: field always present,
>>>> that would be the one that DMARC should have used.
>>> It could have chosen the more complicated, "Sender unless not present,
>>> in which case From". But yes, this bit I get. That said, there are
>>> people who have argued that From: was chosen because Sender: was not
>>> displayed. I think that's a silly argument, but it's one that people
>>> still believe.
>> I'm trying to understand why alignment to any header field is important
>> to DMARC in that case.
>
>
> Because operators have found useful correlations in distinguishing
> between messages that are aligned and being 'genuine' versus ones that
> are not aligned.
>
> In the abstraction of theory, you are correct that it shouldn't
> matter. In the brutality of practice, it appears that it does.
>
We need to consider not just what's a useful correlation today, but what
will continue to be so. As soon as the {spammers, phishers, etc.} catch
on that they can achieve alignment at will, it will cease to be a useful
correlation. History teaches us that will happen quickly.
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