> -----Original Message-----
> From: MH Michael Hammer (5304) [mailto:[email protected]]
> Sent: Monday, September 13, 2010 12:40 PM
> To: Murray S. Kucherawy; McDowell, Brett
> Cc: [email protected]
> Subject: RE: [dkim-ops] BCP for authorizing third-parties ([...] was
> subdomain vs. cousin domain)
> 
> > But I, as a verifier, can't tell that email.americangreetings.com is
> > actually a third party.  It's just another domain to me.
> 
> There is in fact a significant difference between handing your private
> key to a 3rd party and delegating a subdomain. While to you as a
> verifier, it may be just another domain, to myself as a sender and
> signer it is a significant difference in terms of management and
> control.

But don't signers need to have some idea of how the verifiers will handle the 
signatures when deciding how to do such delegations?  Absent any document to 
follow like a BCP for verifiers, you're left to guess at whether a verifier 
will query the DNS further to figure out if it's a delegation to a third party 
or not, and then do enough of those to test all the possibilities.

> > Things like TPA or DSAP attempt to make the delegation of authority
> > visible, but the ones that use DNS mechanisms like CNAME and NS don't do
> > so.
> 
> You are correct. I forget that many in the mail community do not know
> how to use tools such as dig.

I wouldn't go that far, but I'm certain that most or all automated DKIM 
verifiers currently don't bother with any of that.


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