Re: [dmarc-ietf] Ticket #1 - SPF alignment

Alessandro Vesely <vesely@tana.it> Tue, 26 January 2021 11:55 UTC

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From: Alessandro Vesely <vesely@tana.it>
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Subject: Re: [dmarc-ietf] Ticket #1 - SPF alignment
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On Mon 25/Jan/2021 22:35:09 +0100 Scott Kitterman wrote:
> On Monday, January 25, 2021 4:04:33 PM EST Todd Herr wrote:
>> 
>> May I propose that the section labeled "SPF-Authenticated Identifiers" be
>> rewritten as follows:
>> 
>> [...]
>> 
>>    The reader should note that SPF alignment checks in DMARC rely solely
>>    on the RFC5321.MailFrom domain. This differs from section 2.3 of 
>>    [@!RFC7208], which recommends that SPF checks be done on not only the
>>    "MAIL FROM" but also on a separate check of the "HELO" identity. >
> I think this is fine, but there is a subtlety to be aware of.
> 
> If you look at RFC 7208 Section 2.4, when Mail From is null, postmaster@HELO
> is the mail from for SPF purposes.  DMARC really can't change that.
> 
> As a result, there are cases where Mail From results actually are derived from
> HELO and it's unavoidable.


I doubt that SPF filters report envelope-from=postmaster@HELO; more likely they 
write helo=HELO.  In that case, the paragraph quoted above is deceptive.


> I believe the proposed text is clear enough about not using separate HELO
> identity results and that's appropriate.

My filter collects SPF results recorded from an upstream SPF filter.  It writes 
Received-SPF: lines for each identity.  For NDNs, it writes a Received-SPF: for 
the HELO identity only.  Am I allowed to use that result for DMARC?


Best
Ale
--