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Re: [dmarc-ietf] Tree Walk + CNAME

Scott Kitterman <sklist@kitterman.com> Sat, 02 April 2022 23:36 UTC

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From: Scott Kitterman <sklist@kitterman.com>
To: dmarc@ietf.org
Date: Sat, 02 Apr 2022 19:36:24 -0400
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Subject: Re: [dmarc-ietf] Tree Walk + CNAME
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On Wednesday, March 30, 2022 1:06:25 PM EDT John Levine wrote:
> It appears that Tim Wicinski  <tjw.ietf@gmail.com> said:
> >> What should the evaluator do if one of these results in a CNAME that
> >> 
> >> either:
> >>         a) points outside of the tree
> >
> >I would say "Follow the CNAME" - consider LargeCo which points many DMARC
> >records
> >of domains in their portfolio to a record in their main domain.  Or
> >outsourced DMARC to third party.
> >
> >        b) results in a loop pointing at a previously evaluated record
> >
> >CNAME loops are usually detected in resolvers, but loops should return no
> >record found
> 
> Agreed.  There is no need to treat CNAMEs here any differently than they
> are treated anywhere else.
> 
> Like Tim, I can easily see practical uses for a CNAME pointing at a
> shared DMARC record.

I agree.

Scott K

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