[Mailman-Users] DMARC mitigation - was: Templates

[JB]

I can hardly believe I actually followed that whole post start to end!  Thanks Mark.
--------------------------------------------
On Sat, 4/4/15, Mark Sapiro <mark at msapiro.net> wrote:

 Subject: Re: [Mailman-Users] DMARC mitigation - was: Templates
 To: mailman-users at python.org
 Date: Saturday, April 4, 2015, 1:38 PM
 
 On 04/04/2015 09:59 AM,
 Laura Creighton wrote:
 > 
 > ps -- anybody know why all mail I see from
 people on yahoo.com (including JB
 > here)
 arrives to me as from yahoo.com.dmarc.invalid.
 > 
 > It very much seems
 to be a python.org thing, but, ah, why is python.org
 > seeing fit to add this stuff?
 
 
 It's
 DMARC mitigation. Mailman has features for this, but on this
 list
 at least they are turned off. See
 <http://wiki.list.org/DEV/DMARC>
 for
 something about DMARC in general and
 Mailman's mitigation features.
 
 The problem is yahoo.com, aol.com and a few
 other domains publish DMARC
 policies of
 'reject'. For our purposes, this means that a
 message with a
 From: address in one of those
 domains that is not validly DKIM signed by
 that domain will be rejected by a lot of ISPs.
 List transformations will
 break the incoming
 DKIM sig so the only way to get such a message
 accepted by many large ISPs is to munge the
 From: domain in some way.
 
 See the archives of this list from last April
 at
 <https://mail.python.org/pipermail/mailman-users/2014-April/>
 for much
 discussion of this.
 
 Mailman's From: address
 munging will replace, e.g.
 
 From: Mark <mark_sapiro at yahoo.com>
 
 with, e.g.
 
 From: Mark via Mailman-Users <mailman-users at python.org>
 
 and add the original From: to
 Reply-To:, but that doesn't happen with
 python.org mailing lists because the incoming
 MTA at mail.python.org
 deals with this
 differently by just appending .dmarc.invalid to From:
 addresses @yahoo.com, @aol.com and a couple of
 other domains.
 
 Some people
 think this approach is less disruptive than Mailman's
 way -
 i.e. users when replying are astute
 enough to just remove the
 .dmarc.invalid, or
 if not, maybe they'll figure it out after seeing the
 bounce DSN.
 
 --
 
 Mark Sapiro <mark at msapiro.net> 
       The highway is for gamblers,
 San
 Francisco Bay Area, California    better use your sense -
 B. Dylan
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