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Re: [dmarc-ietf] Endless Loops with DKIM reports

"John R Levine" <johnl@taugh.com> Thu, 06 June 2019 08:08 UTC

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Date: Thu, 06 Jun 2019 10:08:44 +0200
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From: John R Levine <johnl@taugh.com>
To: Dave Crocker <dcrocker@bbiw.net>, dmarc@ietf.org
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Subject: Re: [dmarc-ietf] Endless Loops with DKIM reports
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> Taking your note's plain language, you appear to be of the rather peculiar 
> view that specifying standards doesn't matter, since people won't follow 
> them.
>
> Looping is a classic problem.  It has classic solutions.  Getting the details 
> of one specified for this case is, of course, different from getting people 
> to adopt it, but the start is with specifying it.

If people follow the spec there will be fewer loops, but it won't reduce 
the number to zero.  Partly it's because not everyone follows the spec, 
partly because it is hard to anticipate all of the paths that can lead to 
indirect loops a->b->c->a or a->b->c->d->a.

This is hardly limited to mail loops.  The DNS specs say not to create 
CNAME loops, but indirect loops happen all the time so every resolver that 
follows CNAMEs needs loop breaking code.

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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