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Re: [dmarc-ietf] Guidance around constructing an AAR when multiple AR headers are present?

"John R Levine" <johnl@taugh.com> Thu, 25 May 2017 01:38 UTC

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Date: Wed, 24 May 2017 21:37:58 -0400
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From: John R Levine <johnl@taugh.com>
To: Dave Crocker <dcrocker@gmail.com>
Cc: "dmarc@ietf.org" <dmarc@ietf.org>
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Subject: Re: [dmarc-ietf] Guidance around constructing an AAR when multiple AR headers are present?
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On Wed, 24 May 2017, Dave Crocker wrote:
> Unless there is a very compelling need for multiple A-R header fields -- and 
> I don't think I've seen that asserted -- then the simplest thing is to 
> declare them illegal and any occurrence of them as invalidating the 
> authentication mechanism(s).

There's two things going on here.  One is the A-R headers added as an 
incoming message is recieved, the other is the ARC-Authentication-Results 
added by ARC.  Personally, I agree with you that there's no reason to 
allow duplicates of either (it took me about a day to write the mailfront 
plugin that checks SPF, DKIM, and DMARC and adds one A-R header, and I'm 
not that good a programmer), but the horse seems to have left the barn for 
A-R and a lot of sloppy code adds multiple headers for the same message 
hop.

On the other hand ARC-Authentication-Results is new, and we can certainly 
say there's only one of those.

> Really.  The goal here needs to be to make this a simple as possible. It's 
> the only way to get large scale support that interoperates well.

Agreed.

Regards,
John Levine, johnl@taugh.com, Taughannock Networks, Trumansburg NY
Please consider the environment before reading this e-mail. https://jl.ly

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