chris--- via Mailman-users writes:
I've been getting complaints from the Yahoo people that mail is delayed at times, or messages that come out of order.
That could be due to greylisting.
(host mta6.am0.yahoodns.net[67.195.204.74] said: 452 Too many recipients tnmpmscs (in reply to RCPT TO command))
You could try enabling personalization in Mailman. Then each user's message is different, so it will send one per transaction. Depending on negotiation between your MTA and the receiving MTA, this may not be too inefficient because the connection will be reused (aka pipelining). The other possibility would be to tune your MTA to send smaller batches.
However ...
(host mta6.am0.yahoodns.net[67.195.204.74] said: 421 [IPTS04] Messages from 74.112.73.65 temporarily deferred due to unexpected volume or user complaints - 4.16.55.1; see https://postmaster.verizonmedia.com/error-codes (in reply to end of DATA command))
Personalization could exacerbate the problem with unexpected volume depending on how they measure volume (by the number of messages or by the number of recipients). Not much you can do about that except hope they'll learn that sometimes there's list traffic and sometimes there's not.
Have you looked up this error code (IPTS04)?
So it seems that Yahoo/AOL keeps detecting my mailman3 server as either spam, sending too much email, or too many recipients.
I don't think it's detecting spam, or it would say so (or perhaps just blackhole your mail).
Anyone anyone shed some light on how to appropriately solve this issue?
The only real solution is to boot subscribers with AOL/Yahoo/Verizon addresses. That's likely not something you want to do, unfortunately, and subscribers are unlikely to take suggestions that their email provider sucks, and they should change to a competent one, kindly.
Ironically enough, the Japanese government did exactly that in 2014, prohibiting use of Yahoo addresses by government employees or entities -- but yahoo.co.jp is a completely different company from yahoo.com (they licensed the name and the search engine etc), and their email is apparently more competently run, in any case they don't bounce list traffic or cause DMARC problems.