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List:       postfix-users
Subject:    Re: Validation DMARC
From:       Dominic Raferd <dominic () timedicer ! co ! uk>
Date:       2019-11-23 9:26:02
Message-ID: CAF9Mo3L94JWADG8hevyC=fA0ZJ9sGO7aVZNbaFfZhgnzGjH=aA () mail ! gmail ! com
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On Sat, 23 Nov 2019 at 09:14, Roland K=C3=B6bler <rk-list@simple-is-better.=
org>
wrote:

> Hi,
>
> > when validating DMARC, it use the envelop address, or use from address
> from the header?
> it unfortunately uses the from-header.
> (If it would use the envelope address, it would not cause that much
> problems.)
>
> Or in short: DMARC intentionally breaks every mailinglist and every
> mail-forwarding.
> So, if a mail-provider uses a strict DMARC-policy, it effectively
> says: "Our mail-addresses may not be used for mailinglists."
>

DMARC's focus on the From header is absolutely correct because it is about
stopping forging. And it is simply untrue that DMARC breaks all mailing
lists nor that it breaks all mail forwarding.

I realise a lot of people on mailing lists about email have a downer on
DMARC because depending on (a) the implementation of DKIM by the sender's
domain controller and (b) on the setup of the mailing list it can - but
often doesn't - cause problems. But it is a very powerful tool for
preventing forging of emails. Domain controllers who are not bothered about
forging of emails from their domain are not obliged to use it.

[Attachment #3 (text/html)]

<div dir="ltr"><div dir="ltr"><div class="gmail_default" \
style="font-size:small"><br></div></div><br><div class="gmail_quote"><div dir="ltr" \
class="gmail_attr">On Sat, 23 Nov 2019 at 09:14, Roland Köbler &lt;<a \
href="mailto:rk-list@simple-is-better.org">rk-list@simple-is-better.org</a>&gt; \
wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px \
0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Hi,<br> <br>
&gt; when validating DMARC, it use the envelop address, or use from address from the \
header?<br> it unfortunately uses the from-header.<br>
(If it would use the envelope address, it would not cause that much<br>
problems.)<br>
<br>
Or in short: DMARC intentionally breaks every mailinglist and every \
mail-forwarding.<br> So, if a mail-provider uses a strict DMARC-policy, it \
                effectively<br>
says: &quot;Our mail-addresses may not be used for \
mailinglists.&quot;<br></blockquote><div><br></div><div style="font-size:small" \
class="gmail_default">DMARC&#39;s focus on the From header is absolutely correct \
because it is about stopping forging. And it is simply untrue that DMARC breaks all \
mailing lists nor that it breaks all mail forwarding.</div><div \
style="font-size:small" class="gmail_default"><br></div><div style="font-size:small" \
class="gmail_default">I realise a lot of people on mailing lists about email have a \
downer on DMARC because depending on (a) the implementation of DKIM by the \
sender&#39;s domain controller and (b) on the setup of the mailing list it can - but \
often doesn&#39;t - cause problems. But it is a very powerful tool for preventing \
forging of emails. Domain controllers who are not bothered about forging of emails \
from their domain are not obliged to use it.<br></div></div></div>



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