[Mailman-Users] Many users unsubscribed at once (not by me)

[Larry Kuenning]

On 12/13/2015 12:01 PM, Laura Creighton wrote:

>> Have I more or less understood it correctly?
>
> No.  Let us say you have 5 users on your list, user1 at aol.com, user2 at aol.com,
> user3 at aol.com user4 at aol.com and user5 at aol.com.
>
> user1 at aol.com posts a piece of mail to your list.
> mailman tries to deliver to user2, user3, user4 and user5 @ aol.com
> aol says "drop dead, we don't talk to you because of our DMARC policy"
> mail to user2 user3 user4 and user5 bounces.  Their bounce count is
> incremented.

But this account is still incomplete.

Besides what AOL does with the attempted deliveries to user2, user3, 
user4, and user5, you also get problems with delivery to users on a lot 
of other domains.  The reason is that some other domains automatically 
consult AOL to see what to do with mail that claims to come from 
user1 at aol.com but didn't reach them directly from an AOL server.  They 
find that AOL has published a DMARC policy of "p=reject", and they 
obediently follow AOL's instruction to reject the post.  So it bounces 
not only for the other AOL users (2 through 5) but for a lot of users on 
miscellaneous other domains.

The problem originates with AOL's DMARC policy but creates bounces in 
delivery attempts to users on many other domains because those domains 
have decided to respect AOL's published "p=reject" policy.

And Hal's report suggests that this is now happening not only with AOL 
and Yahoo (which started this practice in April 2014) but with messages 
originating on Hotmail as well.  Can anyone check that Hotmail has 
published a "p=reject" DMARC policy?

-- 
Larry Kuenning
larry at qhpress.org