[Mailman-Users] Assistance with altering reply-to behaviours and DMARC

Stephen J. Turnbull stephen at xemacs.org
Fri Aug 28 06:37:18 CEST 2015

Mark writes:

 > First, apologies if this has been discussed before.  I run a number
 > of mailman lists on a Centos 6 platform and mailman 2.1.12-25. This
 > version was updated in July as follows:
 > https://rhn.redhat.com/errata/RHSA-2015-1417.html and included
 > fixes for a number of DMARC issues.  Including "... With this
 > update, domains with a "reject" DMARC policy are recognized
 > correctly.."

Stock Mailman 2.1.12 doesn't do any DMARC detection.  This is quite
bizarre that they would backport such a feature rather than update to
2.1.18-1 or later.  Mailman 2.1 is hardly an unstable package.

 > Normally the lists we use are configured with reply_goes_to_list
 > and anonymous_list is off.  We have done some testing, and we have
 > not been able to identify settings that will retain
 > reply_goes_to_list functionality and turn on DMARC Mung.

You'll have to talk to the vendor who did the modifications.

 > Generally what happens is that the first message is successfully
 > sent to a yahoo.com address and this user can reply to the message
 > as normal.  However, mailman adds the original sender to the
 > reply-to meaning that when another user replies to this message
 > reply_goes_to_list doesn't work.

What do you mean by "doesn't work"?  That it doesn't go to the list at
all, or that although it goes to the list, it *also* goes (separately)
to the original poster?

Not going to the list at all means the MUA is broken IMO; multiple
addresses in Reply-To are explicitly allowed by the RFC, and MUAs
should reply to all of them.

 > It seemed to me that a small modification to CookHeaders.py could
 > prevent the adding of the original sender email to "Reply-To"
 >          # We also need to put the old From: in Reply-To: in all cases.
 >          if o_from:
 >              add(o_from)
 >          # Set Reply-To: header to point back to this list.  Add this last

After disabling the "add(o_from)" operation, if reply_goes_to_list is
set, then (1) the reply goes *only* to the list by default, and (2) it
is impossible for the user's MUA to automatically format a reply to
poster.  If reply_goes_to_list is not set, (1) reply by default will go to
list (since it's the address in From), and (2) it is impossible to
automatically format a reply to poster.

It is our opinion that (2) is a sufficiently important bug that we are
unlikely to change this, even to provide an option.  But if you want
to make that edit, it probably does what you want.  Depending on your
users, you may or may not get complaints about inability to respond

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