Re: [spfbis] Question about SPF checks based on RFC 7208

Scott Kitterman <> Mon, 02 May 2016 02:55 UTC

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From: Scott Kitterman <>
Date: Sun, 01 May 2016 22:55:35 -0400
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Subject: Re: [spfbis] Question about SPF checks based on RFC 7208
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While I believe your assessment of the type of records that do this is correct 
(mx would have been next on my list to deprecate after ptr if I thought we 
could have pulled it off), I think it's only technically correct to count an mx 
as void if you've checked both (and that's what RFC 7208 already says).

We may want to make that clearer, but changing it so that only A or AAAA 
missing counts as void would be a technical change that has interoperability 
risks.  I don't think we should do it.

Scott K

On Sunday, May 01, 2016 10:43:33 PM Stuart D. Gathman wrote:
> Implementations will *always* lookup only one of A/AAAA - the type
> matching the connect IP.  So taking your second option would mean that
> A,MX mechanisms would never be void!
> On Sun, 1 May 2016, Scott Kitterman wrote:
> > I think it might make sense that to clarify that an mx mechanism is only
> > void if neither A nor AAAA exist.  Implementations could either do the
> > extra lookup or just not count it as void if only looking up one.  From
> > an interoperability perspective, I think either would be fine.