Re: (DMARC) We've been here before, was Why mailing lists (Martin Rex) Thu, 17 April 2014 20:23 UTC

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Subject: Re: (DMARC) We've been here before, was Why mailing lists
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To: Douglas Otis <>
Date: Thu, 17 Apr 2014 22:22:59 +0200 (CEST)
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From: (Martin Rex)
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Cc: Pete Resnick <>, John R Levine <>, "" <>
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Douglas Otis <> wrote:
> Martin Rex <> wrote:
>> MUAs which are not implementing the rfc822/2822/5322 "on behalf of"
>> semantics of a message that carries both From: and Sender: header
>> fields ought to be FIXED.  Standards that build on rfc822/2822/5322
>> and do not respect "on behalf of" semantics of messages with
>> both "Sender:" and "From:" also need to be FIXED.
> Merging Sender and From header fields by MUAs offers no protection
> when actual sources of messages remain unknown.

This is *NOT* about protection or authentication, this is purely about
rfc822/2822/5322 message semantics.  Something that has been well-defined
and constant for decades.

At the beginning of this Email there are two quotations with assertions
of authorship.  There really is no difference to the name in the From:
field of an EMail that is carried with a different Sender (and envelope
MAIL FROM:) through an SMTP transport system.

There is no difference in semantics between the assertions above
and the rfc822-header assertion in "From:", when an rfc822 message
is transferred through an SMTP MTA system in an "on behalf of" scenario
with a differing Envelope "MAIL FROM" & matching Sender: rfc822-header.