DMARC/DKIM mitigation on maling lists

Wed Nov 8 04:43:45 PST 2023

This is not really related to dealing with DMARC, but I noticed
something in your message.

Here are the headers in the messaeg, minus a couple added by my system
(spam filtering scores) omitted to reduce noise.

  - Your message has a From: of neteler at osgeo.org.
  - it was actually sent via google.
    * google did not include your client's IP address (that's great)
    * google has an X-Google-DKIM-Signature instead of DKIM-Signature
      (This is bizarre but not news to me)
    * google's faux DKIM header is from 1e100.net
      (also odd but not news)
  - osgeo.org applied a dkim signature from osgeo.org to the list
    message

This last point is normal in many ways; it signs the mail as coming from
osgeo so that people can

welcomelist_from_dkim	*@*	osgeo.org

to not filter things coming from the list.  However, your message did
not actually come from osgeo.org, it seems, and thus really shouldn't
have gotten a fresh DKIM signature.

What you are doing is of course totally normal, but in the world of
DKIM/DMARC (and then ARC) that I think we are heading to, outgoing mail
has to be handled by the outgoing MTA of the domain, and not sent via
some other domain's MTA.

This is particularly an issue for people with secondary email addresses,
like this case.

MIME-Version: 1.0
References: <002a01da075d$776917e0$663b47a0$@pcorp.us>
 <rmi34xy1y0k.fsf at s1.lexort.com>
 <002b01da075f$893ec210$9bbc4630$@pcorp.us> <rmir0lizekw.fsf at s1.lexort.com>
 <003401da078b$d7e29410$87a7bc30$@pcorp.us> <ZTpWzZ4Qvri1CFmb at c19>
 <ZTty0VH3w3kmuGIT at c19> <rmizfzzinds.fsf at s1.lexort.com>
 <8ef85620-59d4-40c8-ac7e-07af8ba3aa09 at betaapp.fastmail.com>
 <ZUoZAzLW4b/6w+AI at c19> <ZUtvhmhiRTGb/Bhe at c19>
In-Reply-To: <ZUtvhmhiRTGb/Bhe at c19>
From: Markus Neteler <neteler at osgeo.org>
Date: Wed, 8 Nov 2023 13:12:20 +0100
Message-ID: <CALFmHhsecrhbhECRAj5sDTJtA2o1+dZncxt--SrMbVG8Wq4=_g at mail.gmail.com>
Subject: Re: DMARC/DKIM mitigation on maling lists
To: sac at lists.osgeo.org, jmckenna at gatewaygeomatics.com, howard at hobu.co,  lr at pcorp.us
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