Re: DMARC: perspectives from a listadmin of large open-source lists

Dave Crocker <> Tue, 08 April 2014 12:50 UTC

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Date: Tue, 08 Apr 2014 07:48:03 -0500
From: Dave Crocker <>
Organization: Brandenburg InternetWorking
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To: Sabahattin Gucukoglu <>, "Robin H. Johnson" <>
Subject: Re: DMARC: perspectives from a listadmin of large open-source lists
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On 4/8/2014 2:13 AM, Sabahattin Gucukoglu wrote:
> On 8 Apr 2014, at 06:16, Robin H. Johnson <> wrote:
>> And don't start on suggesting Reply-To instead, RFC 2822 already
>> noted that it should be set by the author, not the list software [1].
> Not that I disagree, but be sure to read the note in RFC 5598 s5.3.

Section 5.3 has no "note". I assume you mean the portion on mailing lists:

      5.3. Mailing Lists
       RFC5322.Reply-To:  Set by - Mediator or original Author

          Although problematic, it is common for a Mailing List to assign
          its own addresses to the Reply-To: header field of messages
          that it posts.  This assignment is intended to ensure that
          replies go to all list members, rather than to only the
          original Author.  As a User Actor, a Mailing List is the Author
          of the new message and can legitimately set the Reply-To:
          value.  As a Mediator attempting to represent the message on
          behalf of its original Author, creating or modifying a
          Reply-To: field can be viewed as violating that Author's
          intent.  When the Reply-To is modified in this way, a reply
          that is meant only for the original Author will instead go to
          the entire list.  When the Mailing List does not set the field,
          a reply meant for the entire list can instead go only to the
          original Author.  At best, either choice is a matter of group
          culture for the particular list.

To the extent anyone wants to claim that this is in conflict with RFC 
5322, it's helpful to remember that a mailing list is a 'mediator' and 
not an MTA.

So it took delivery of a message and is posting a /new/ one.  In formal 
terms, the "author" of the new message is the mailing list; hence it 
gets to set Reply-To...

Consequently, the ending clause in "it should be set by the author, not 
the list software" is not correct.


Dave Crocker
Brandenburg InternetWorking