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

[Laura Creighton]

In a message of Sun, 13 Dec 2015 13:42:47 +0100, Hal writes:
>On 13/12/2015 13:05, Jayson Smith wrote:
>> Hi,
>>
>> Unfortunately, disabling automatic removal from the list will only fix
>> one effect of the problem, not the problem itself. There's something
>> going on which is causing mail to those addresses to bounce. If you are
>> receiving messages with the subject of "Bounce action notification"
>> these will tell you who is bouncing mail, and the attached mail delivery
>> failure reports will tell you why they are bouncing mail, which is
>> important. I suspect you have a DMARC or IP reputation issue.
>
>I'm not sure I fully understand this and what to do about it.
>
>Are you saying that even though I turn "automatic removal" off I will 
>still have postings from certain list members NOT reaching the list (but 
>bouncing with an error message back to me, the list owner -possibly also 
>with an error alert to the poster as well)?

This is possible.  What is more likely is that a member of your list,
posts something to the list.  Then mailman tries to deliver the mail
to all the subscribers.  When it calls up some_site asking to deliver
mail to subscribers who have subscribed from accounts on some_site,
some_site says something to the effect of:

Drop dead.  We are protecting our users from receiving mail from
you!  No matter how many times you ask us to send mail to them,
we _won't_ because _we don't like you and your crappy mailing list_.

So you need to check your logs and find out if there is a some_site,
or more than one some_site which really doesn't like you.

The usual reasons for disliking you are:

1. We hate your IP, you have bad reputation with us, maybe you have been
   reported as a spammer someplace, or maybe you just send us a lot of
   mail and we don't like that.

Mailman cannot do anything about this problem.  Talking to the site that
hates you can, if the site that hates you is willing to talk to you at
all about the problem.  Large sites, like aol typically do not.   "We
hate you because you are a spammer, and the last thing we want to do
is to tell you how to get around our spam protection.  We don't care
how many innocent non-spammers are hurt by our policies which has falsely
caused them to be considered spammers.  So if you aren't a spammer,
too bad, we won't lose any sleep over the fact that your mail cannot
arrive here.  And we won't talk to you about it, either."

2.  We have a DMARC policy which is designed as follows:

    If mail comes in that originates from a user on one of our sites,
    and it doesn't come in on one of our servers, we will call this spam
    and refuse to deliver it.

The big offenders here are aol and yahoo.  This policy breaks every 
mailing list on the planet.

A user on yahoo.com sends mail to a mailing list, and the list tries
to send it to all the subscribers, and when it tries for all the other
subscribers at yahoo.com, yahoo says, 'This mail that supposedly
came from user at yahoo.com, didn't come from one of our servers. Do
not deliver.'

If this is your problem, and we think it is, you need a mailman 
at least 2.16 and 2.18 is better.  Then we can tell you how to
configure it to rewrite things so that your mailing list mesages
no longer appear to come from their senders, so yahoo doesn't
reject them, but does let people reply to such messages and
have the reply go to the real sender, at yahoo or wherever
the way that you expect.

But first you have to figure out why you are getting the bounces
in the first place.  Check your mailman log files for that.  They
are in different places depending on whether you have a CPanel
mailman, or a regular one, or one of countless other hosting
solutions that I am unfamiliar with.

Does this make sense?

Laura Creighton