I feel really stupid asking this question, but I recently signed up to a GNU mailman list for the first time ever and can't quite figure out how to interact with it properly. I can't find any documentation anywhere on how to participate as a list member. In particular, I am trying to figure out how to make my responses nest properly when replying from a Gmail account. Through some sparse info I've gleaned, I found that the "In-Reply-To" header is supposedly the one that determines where your message nests on the list.
So, I posted a new message to the list, and when somebody replied to me, I received a copy in my Gmail in addition to the post on the list archives page. I replied to the Gmail and addressed it back to the main list address. After sending, I examined the Gmail headers, and In-Reply-To was indeed set to the Message-ID of the person who had replied to me, so I thought my response would be nested under his. Unfortunately, it was not. It was nested underneath my own OP, next to his. I can't figure out why, except that there is another header References, which in my response, included two Message-ID's, both the one from my original post, and the one from the first response.
None of this stuff is intuitive at all or explained anywhere that I can find, and Gmail of course gives you no control of email headers... but I don't want to switch to an entirely new mail service just to interact with a Mailman list. Nor do I want to spam a real list with a bunch of stupid test messages of me figuring out what is probably supposed to be a very simple system. Does anybody know of a test instance of mailman somewhere that I can send a few mails to just so get this all sorted out? I found what appeared to be a couple, but none of them were actually accepting mail.