Re: [dmarc-ietf] non-mailing list use case for differing header domains

Alessandro Vesely <vesely@tana.it> Tue, 28 July 2020 15:59 UTC

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From: Alessandro Vesely <vesely@tana.it>
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Date: Tue, 28 Jul 2020 17:59:17 +0200
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Subject: Re: [dmarc-ietf] non-mailing list use case for differing header domains
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On Tue 28/Jul/2020 17:22:41 +0200 Laura Atkins wrote:
>> On 28 Jul 2020, at 16:14, Alessandro Vesely wrote:
>> On Tue 28/Jul/2020 11:07:19 +0200 Laura Atkins wrote:
>>>> On 28 Jul 2020, at 08:36, Alessandro Vesely wrote:
>>>> On Tue 28/Jul/2020 08:54:02 +0200 Autumn Tyr-Salvia wrote:
>>
>>>>> # The resulting message uses executive@secondbrand.com in the
>>>>> friendly From: field, but firstbrand.com <http://firstbrand.com>  in
>>>>> the SMTP MAIL FROM domain, so the headers are no longer aligned for
>>>>> SPF. >>>>
>>>> Heck, can't they DKIM sign?
>>> This really misses Autumn’s point. [...]
>>> Autumn has presented a very real world scenario that demonstrates the
>>> overall complexity of mail management operationally. Your solution “sign
>>> with DKIM” has significant barriers to adoption. For instance, assume that
>>> there is code installed on the mailserver that will grab the 5322.from
>>> address and sign with the appropriate DKIM key. How many domains are
>>> involved? How many different mailservers? How long will this solution take
>>> to deploy? Banks do not move quickly and, for the obvious reasons, any
>>> changes to security require multiple reviews and assurances that the
>>> implications are understood.
>>
>>
>> If the bank delegates a subdomain to each trusted subsidiary, each
>> subsidiary could manage their keys on their local DNS and email servers.
>> If the bank can afford "relaxed" DKIM alignment, they can sign with 
>> d=local-branch.bank.example and From: transactions@bank.example. What's
>> the risk of doing so? >
> That does not address the problem Autumn brought up at all.


I understood the problem is the lack of agility.  Delegation to smaller domains 
using local servers would solve it, wouldn't it?  Even with many domains...

What am I missing?


Best
Ale
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