[MlMt] Too many bounces?

Benny Kjær Nielsen mailinglist at freron.com
Mon Jan 28 03:35:27 EST 2019

On 27 Jan 2019, at 18:06, Robert Brenstein wrote:

> Such notifications are most often prompted by the sending host, that 
> is the list host, suddenly deemed to be a spammer.

This could be the problem, but I don't think this is the case. I use a 
third party service to monitor the reputation of my server and it has 
had no problems.

> Usually, it is a side-effect of some other user of that same service 
> causing the IP (IP range) to be blacklisted. In this case, it might 
> have been only Google thinking so, rightfully or not. Google, AOL, a 
> few other services also count the number of recipients in each 
> instance of mail and if they adjusted that limits, blacklisting would 
> be the result.

The issue seems to at least partly be caused by at least 1 user using 
the DMARC `reject` option. All users on email servers which respect this 
option (Gmail, iCloud, ...) are going to bounce emails from such a user. 
These bounces are going to add up on my server (there's a MailMan score 
system for this) and when it reaches a certain limit they are 
“unsubscribed” (they are actually only disabled at first).

I'm deliberately trying to be vague here. When googling the subject you 
might notice that any statement about SPF/DKIM/DMARC is quickly followed 
by discussions about how things really work -- in theory or practice. 
I'm now at the point where I would automatically become suspicious if 
anyone (any webpage) seems to claim to fully understand the consequences 
of any kind of setup/setting related to this :-)

As a short term solution I've now disabled bounce processing on my 
mailing list software. This is mainly a problem for me and not my users. 
This won't change the fact that some emails (at least from 1 user) is 
not going to be received by a lot of other users.

If you want to see if you missed a reply to one of your emails then look 
here: https://www.mail-archive.com/mailmate@lists.freron.com/

Data point: 89 mailing list members out of 474 have been unsubscribed 
(some have probably resubscribed now).

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