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Re: [ietf-smtp] Email explained from first principles

John Levine <johnl@taugh.com> Mon, 24 May 2021 14:03 UTC

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Date: Mon, 24 May 2021 10:03:14 -0400
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From: John Levine <johnl@taugh.com>
To: ietf-smtp@ietf.org
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Subject: Re: [ietf-smtp] Email explained from first principles
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It appears that Kaspar Etter  <kaspar@ef1p.com> said:
>2. List-Name header field: Mailing lists shouldn’t rewrite the messages of others and break DKIM signatures in the process.

Sorry, but this shows some serious misunderstandings about both DKIM and mailing lists.

DKIM is a transport signature, which in this case shows that the message was sent from the author
to the mailing list system.  List apply their own DKIM signature on the mail they send.
Mailing lists have been editing messages for 40 years, long before anyone
ever thought of DKIM or DMARC.   It is a well known DMARC failure that it doesn't work with mailing lists.
Some people have tried to rewrite history and claim that it is the lists' fault but they are wrong.

The whole point of ARC is to provide recipient systems with info to help recognize when they should
ignore DMARC and deliver mail from lists and other legitimate senders that don't happen to match the
assumptions that DMARC makes.

R's,
John

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