Steven Owens writes:
Also, confusing the issue was the fact that my gmail account is receiving other list messages, but not list messages from those users, and there was no sign of a bounce from gmail. However, I did some googling and apparently it's not unknown for gmail to silently discard messages... sigh.
I sympathize with your desire for more information, but it's not that simple.
A silent discard (or with report to DMARC Author Domain, not you or author, if requested by that domain) is correct and courteous behavior if Google can't confirm origin of your message.
Otherwise the bounces produce backscatter. Spammers are known to fake every header under the sun, but they can't fake SPF or DKIM.[1] It is not known precisely what Google's criteria are, but we do know that Google ignores DMARC p=reject for at least some mailing lists. However, I suspect that they want crypto proof of origin -- that means they can send the bounce to somebody who provably handled the message. Without DKIM or SPF, anywhere they send the bounce might be based on a spoofed address.
So the question posed elsewhere about whether your site provides DKIM and SPF, or not, becomes important. If not, you should do so as soon as possible -- that's the best way to improve reliability of delivery and receive bounces.
I was going to ask if there's a log level setting that I can turn up, but google shows you replying to a similar request with "no" :-).
What are you hoping to see logged? Maybe it could be added.
Footnotes: [1] Of course they sometimes can and do suborn the hosts that provide the signatures. I'm excluding that from "fake".