John Levine wrote:

>>John Levine wrote:
>>
>>> This would be a good time to reread RFC 7489, particularly section
>>> 6.6.3, and very particularly numbered item 3 in that section.
>>
>>This is simply the DNS record discovery mechanism. It doesn't explain the 
>>apparent overriding of the behaviour of
>>the sub-domain policy specified in the record discovered via that mechanism.
>
> Hmmn.  I wonder if anyone ever tested sp=none.  More typically you
> don't expect your subdomains to be sending mail so it's sp=reject.

Actually, this is a good point: setting aside any apparent inconsistency 
between the language of the specification and the response of gmail, it's not 
at all clear why "p=reject sp=none" would ever be a good idea. There may be 
specific cases where it may make sense to carve out a single sub-domain with a 
weaker policy for specific, closely-monitored purposes, but this would seem 
better addressed by creating a policy specific to that subdomain, rather than 
publishing a blanket policy which effectively says "You can't impersonate our 
domain, but create any subdomain you like and impersonate your heart out!".

Can anyone see any good reason to use a policy like this?

Petr, can you describe what you were trying to achieve?

(I'm not advocating a specification change, just surveying likely use cases.)

- Roland
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