Re: EAI and ADSP/DMARC

On 9/12/2012 12:46 PM, John Levine wrote:
>>> A correct implementation of DMARC will reject emails at the edge as per
>>> sender policies.
>>
>> You mentioned about ten big implementers. Are all correct in this
>> regard? (Just curious.)
>
> I think they all do the filtering in the SMTP session.


Given the DMARC sits on top of DKIM evaluation, the only place DMARC 
processing can be done during the SMTP session is after the DATA 
command.  No doubt, some/all of the major users of DMARC have put their 
code there, for the reason you cited.

That said, DMARC follows the usual model of making a distinction between 
giving a sending-side a means of expressing its desires, versus 
mandating what the receiving-side does with it.

In order to achieve protocol interoperability, a spec can dictate the 
behaviors of both sides.  Outside of that requirement, a receiver is not 
going to be "told" what to do by a sender.

The receiver might choose to pay attention to the receiver's wishes, but 
that's quite different from claiming that a failure to adhere to a 
sender wishes constitutes an "incorrect implementation."

d/

-- 
  Dave Crocker
  Brandenburg InternetWorking
  bbiw.net
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