Rich Kulawiec on 20 Jun 2019 15:40:35 -0700

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Re: [PLUG] excessive bounces for PLUG

On Wed, Jun 19, 2019 at 06:56:29PM -0400, Ronaldo Nascimento wrote:
> I have received 2 of these messages in the last week. My PLUG email is
> Gmail, so I don't know if its an issue with Gmail itself.

In all likelihood, these have the same root cause as was discussed
in the thread "Puzzling confirmation request" about a week ago.
Briefly, and oversimplifying to the point of error, your mail hosts
are publishing mail system policies which state that mail claiming
to be from their domains is only valid if it comes from their own
mail servers.  Thus mail which is gatewayed (unchanged) through a
mailing list is marked as invalid by recipient systems which check
it against those policies.

Here is an old but succinct summary of the situation:

	Yahoo breaks every mailing list in the world including the IETF's

This is allegedly being done to decrease spam, but the effect that it
has on spam is negligible at best.  (Note that I receive spam all day
every day from the operations who deployed this first.)

This is allegedly being done to decrease forgeries, but when an operation
like Yahoo has *every single one* of its user email accounts compromised,
that's not really happening either.  (And if you think other freemail
providers are doing markedly better, I have a bridge available at low cost.)

This has as one of its unfortunate side effects that it breaks mailing lists,
never mind that mailing lists are where the heavy lifting gets done and that
they predate most of these operations by decades.

The fix -- well, band-aid, really -- is to upgrade to the latest version of
Mailman and turn on appropriate DMARC mitigation AND to make sure everyone
on the list is aware of the consequences of that, because some of them
are user-visible.  I offered a week ago to help with that, but received
no response, so I'm going to offer again.

If this fix isn't applied, then this will steadily get worse.  Some of
you are already not receiving messages originated by some members of this
list.  These bounces will be counted, Mailman will automagically suspend
delivery to some subscribers once the count increments to a preset number,
then it will unsubscribe people, Zuul will make you choose the form
of the destructor, etc.


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