[Mailman-Users] DMARC and Bellsouth, etc.

Lindsay Haisley fmouse at fmp.com
Wed Apr 16 18:51:24 CEST 2014

I'll jump in here and offer the quick solution that I'm using at FMP.
The primary culprit here is Yahoo, which publishes a DMARC p=reject
policy via DNS.  To the best of our knowledge, so far, no one else is
doing this, although sbcglobal, att.net, comcast.net, Hotmail and a
number of other email service providers will honor Yahoo's policy and
bounce posts which have a yahoo.com address in the From header and come
from an IP address which isn't a yahoo.com server.  This is the case, as
per relevant RFCs, for most mail from Mailman mailing lists.

What I'm advising list admins here, which puts a band-aid on the
problem, is to put all yahoo.com subscribers on moderation, effectively
making them read-only subscriptions.  Also go through your membership
list and clear any nomail disablements with a "[B]" beside them.  We're
also advising yahoo.com list subscribers to get a Gmail account (as free
and easy to get as a Yahoo account)

Mark or Stephen may have a more in-depth response to you, but this is
how I've addressed the problem here.

On Wed, 2014-04-16 at 11:30 -0400, Jose I. Rojas wrote:
> We have a community group mail list which we run using Mailman and
> have lately had a problem getting our emails to members who have
> Bellsouth and Yahoo email addresses. I've seen the posts about DMARC
> but am not that tech-savvy to figure out what this means and how to
> resolve. Some of our members have complained that they are not getting
> the group's emails. We have written Bellsouth but they claim the
> domain is not on a blacklist and problem is not on their end. Our ISP
> tells us domain is "RFC -compliant" and problem must be with Bellsouth
> or Yahoo. How do we resolve this?  What is the fix? Help, please...

Lindsay Haisley       | "Everything works if you let it"
FMP Computer Services |
512-259-1190          |          --- The Roadie
http://www.fmp.com    |

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