[Mailman-Users] Emails from yahoo members, are getting rejected by yahoo, "Service Unavailable".

Jim Popovitch jimpop at gmail.com
Tue Apr 15 01:54:16 CEST 2014

On Mon, Apr 14, 2014 at 7:28 PM, Larry Stone <lstone19 at stonejongleux.com> wrote:
> On Apr 14, 2014, at 5:51 PM, Jim Popovitch <jimpop at gmail.com> wrote:
>> On Mon, Apr 14, 2014 at 3:16 PM, Lindsay Haisley <fmouse at fmp.com> wrote:
>>> So what is being said here?
>> When a yahoo poster sends an email to your list, that email is
>> reflected to the rest of the other subscribers.  Those other
>> subscribers may or may not check yahoo's dmarc policy before accepting
>> your list email.  If they do reject your list message, then that
>> equals 1 mailman bounce.  After a few posts from yahoo members, the
>> bounce scores increase and the other subscribers are unsubscribed.
> I think most of us are clear on that point. Where I’m confused (and I’m thinking that’s what Lindsay is asking about) is where you said
>> Yes!  (maybe start reading threads from the bottom up?)   :-)

Ahh, my "Yes!" post to Joe was because earlier in the day I had stated
one thing about dmarc, and then Mark corrected me, and at that time I
acknowledged Mark's correction.  And then along comes Joe the next
day, and he replied to my incorrect statement before he read my later
post.  In threaded message format, the bottom post would generally be
the latest post, thus my comment.

Back to DMARC, one thing that wasn't clearly stated earlier, wrt
DKIM+SPF, Mailman "breaking" the DKIM because of header+body
modifications.  Whether or not a remote dmarc validation checks the
SPF record (of the From: address) is dependent on the posters  dmarc
aspf setting (which *may* tell receivers to honor the poster's DKIM
*and* SPF record).  So even passing the DKIM signed portion,
unfettered, may still fail dmarc checks at a receiver, resulting in
bounces (and of interest to privacy advocates, the failed dmarc check
will most likely send a copy of the post onward to various other
organizations listed in the dmarc rua and ruf records).

The only true ways to handle dmarc messages (imho) are to reject posts
where the poster's domain clearly says to not forward (i.e.
p=reject)... OR... totally wrap the poster's email as an attachment
and change the From: to something under control of the mailinglist
that is sending the email.

-Jim P.

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