Hello friends. We are using Mailman through Dreamhost, which doesn't allow us to change server-based list configurations, we only have access to the Admin's normal Options pages.
After years of working fine, we'd recently been having bouncing problems specifically with gmail addresses.
Thinking this was Dreamhost's problem, and not mine, I queried Dreamhost support, and they looked over a bounced message. Their suggestions are pasted below. I changed from_is_list to Munge From but now the reply to headers have both the list address and the original sender's address. So I assume the original sender gets sent two copies of responses, one from the list and the other directly to them.
I've spent some time over the years trying to train them to not use Reply to All to avoid that double message situation, and now it's happening even with just a regular Reply.
I'm hoping I can fix this easily. I know a little about this stuff, but I'm basically just a list manager, not a full-on sysop, so please be gentle in your terminology and instruction.
From Dreamhost support:
Taking a look into the 're-wrenches-re-wrenches.org' list, the bounce errors point to possible DMARC issues with the list post going out. But, the 're-wrenches-re-wrenches.org' list does not look to have 'Munge From' enabled on the list right now, so you'll want to log into the list and enable that on the 'General Options' page for that list.
Along with that, the list sub-domain didn't have our SPF, so I've added it for you since the domain is managing DNS services with us as well:
lists.re-wrenches.org. 300 IN TXT "v=spf1 mx include:netblocks.dreamhost.com include:relay.mailchannels.net -all"
That was setup on the 'Websites' > 'DNS Settings' page on your account for the 're-wrenches.org' domain.
Having both above set will help to better the outgoing relays of the posts, so set the 'Munge From' and let us know if you're still seeing the same bounce as before.