Re: DMARC methods in mailman

Theodore Ts'o <> Wed, 21 December 2016 15:12 UTC

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Date: Wed, 21 Dec 2016 10:12:18 -0500
From: Theodore Ts'o <>
To: Philip Homburg <>
Subject: Re: DMARC methods in mailman
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On Wed, Dec 21, 2016 at 01:10:16PM +0100, Philip Homburg wrote:
> >The focus has been on Yahoo because of a message which was posted 
> >several years ago.  I collected some statistics for an IETF mailing 
> >list.  Approximately 40% of the subscribers are using [1] DMARC; most 
> >of then are not using Yahoo.
> Are you talking about senders or recipients? The reason yahoo stands out is
> because yahoo seems to be one of the few providers that rejects or bounces
> mail that fails DMARC checks.
> Or are you saying that at the moment 40% of the subscribers of IETF lists reject
> or otherwise not receive mail from DMARC protected senders?

It's much more likely that this is the percentage of subscribers that
are sending from domains that are claiming a DMARc policy.  What's
interesting is how few of these domains are actually *following* the
DMARC specification in rejecting, unconditionally, e-mails which fail
the DMARC checks.

Which to me shows how defective by design DMARC really is; even many
of the proponents of DMARC are running mail systems which are not
honoring the DMARC "specification".

Given that the DMARC "specifcation" isn't even being treated as a
standard that must be obeyed in all of its particulars by its
proponents --- the fact that this is being used by its propoonents to
twist mailers of the IETF --- a standards body --- into knots because
it is enforcement is random and *not* standardized is, quite frankly,
amazing to me.

Let the employees of those companies which are proponents of DMARC
suffer.  And they might not be suffering that much given that at least
one of those companies isn't really enforcing DMARC on the receiving
end for their users....

					- Ted