I agree with this analysis. I have had issues in the past where some big email providers allowed the first few through and then started returning an error for everyone else in the same domain. It was fairly obvious from the MTA logs (postfix in my case) when this was happening — fixing it was rather trickier, since ultimately it’s overzealous anti spam policies at the mail provider which are the cause of the trouble.
Postfix is a bit of a pain for configuring domain-specific delivery behaviours; it has global settings smtp_client_connection_count_limit and smtp_client_connection_rate_limit, which might be helpful, but it’s hard to make them different for different domains. Exim would be much simpler to configure to do that. One day when my bag of round tuits gets bigger I might switch back to Exim.
Tim
On 12 Jul 2022, at 13:52, Stephen J. Turnbull <stephenjturnbull@gmail.com> wrote:
Julian Kippels writes:
This was not a problem on Mailman 2, but has become a problem on Mailman 3. It seems to me that for example Mailman 3 sends mails to the first 5 existing member addresses from domain A, then encounters several (20 or so seems to be the threshold) "dead" member addresses from domain A that generate a bounce and then does not even attempt to reach the remaining 800 member adresses from domain A and only sends to members on domain B and domain C.
"Seems to you"? Do you have logs and empty MTA queues etc as evidence for this, or just mail not arriving at the subscription addresses? What are the configuration settings for the list, most importantly, are messages personalized?
In the default configuration without personalization, I think this is very unlikely to be Mailman's problem. Mailman will send a reasonably large number (specifically, 500) of recipients for the message, and then send the message itself once. In this case, if only a couple dozen recipients of 800 receive the message, it's either the recipient MTA or some interaction between your MTA and theirs, not Mailman. Check the MTA outgoing queue and MTA logs.
If the list has enabled personalization, so that the footer (usually) contains subscriber-specific information, then there is only one recipient per message. However, the interaction you describe is unlikely to be due to Mailman's behavior in that case as well, as Mailman tracks bounces by individual address, not by domain. It's not useful to do so, as almost all bounces that reach are address-specific. If there is a problem in connecting to a remote host, that is almost always handled by the MTA and Mailman never finds out about it. Again, check the queue and the logs for the MTA as well as for Mailman.
On the other hand, I was talking with the postmaster of a rather large site recently, who was complaining about freemail G. What happens is that with a very large list with many bouncing addresses, the sending MTA builds up a backlog of undelivered messages. The MTA tries to resend them at intervals (or for some MTAs the next time a message goes out to that domain). Of course since it's a mailing list, the same addresses bounce, and now you have *twice as many* undelivered messages waiting to be delivered. Pretty soon you have a very large number of attempts within a very short time (in the case of my postmaster acquaintance, an average of 3/second), and freemail G treats that as a DOS attack and starts refusing or delaying connections.
That sounds a lot like what's happening to you. Without the log and configuration information it's not possible to be sure, but your hypothesis isn't very consistent with the way Mailman actually does its work.
Is there a way to globaly ignore bounces and
No. That's one of the better ways I can think of to acquire a reputation as a spammer and generally bad actor.
send out mails to all members of a list, no matter what?
That is what Mailman does. Only after it has received "enough" bounces for a particular user does it disable delivery to that user only. Mailman does not keep records of bounces per domain.
Steve
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