Re: [Evolution] [Fwd: You have been unsubscribed from the evolution-list mailing list]

[Ángel González <angel 16bits net>]

On 2016-07-29 at 15:24 +0100, Patrick O'Callaghan wrote:
> It's tempting to think so, but there are also users with pacbell and
> bellsouth addresses who have similar problems. I note that both of them
> route their mail through prodigy.net, if that means anything.
>
> poc

Apparently, prodigy.net email service is actually provided by yahoo;
https://en.wikipedia.org/wiki/Prodigy_(online_service)#A_public_company


So it is really just yahoo having problems with emails from their own
customers that passed through a mailing list.


I got the hint by the error message given by the prodigy mailserver
when attempting to spoof a yahoo From:
> <<< 554 5.7.9 Message not accepted for policy reasons.  See 
> https://help.yahoo.com/kb/postmaster/SLN7253.html
> 554 5.0.0 Service unavailable


I'm quite sure it is related to their DMARC reject policy (perhaps even
marked internally).

It asserts that yahoo.com emails will only ever come from yahoo
servers, and non-complaint emails shall be *rejected*. This makes
complete sense for eg. paypal.com but for a free mail provider like
yahoo imho such policy is broken. Precisely because it completely
breaks mailing lists:
https://en.wikipedia.org/wiki/DMARC#Mailing_lists


Also, it should be noted that other providers may also be taking that
into account. For instance gmail accepts those DMARC-failing messages,
but they are sent to the Spam folder.

There are a few options in recent mailman versions for handling this,
although none seems specially appealing:
https://wiki.list.org/DEV/DMARC


Best regards