Last night, when I changed the DNS for agoranomic.org to point to GitHub Pages, I forgot to change the MX record so that my server would continue to receive mail. I knew I had to do that, but it slipped my mind... Thus the lists were down for several hours, until this morning when I saw an email from o and fixed it. Sorry.
In other news, the DNS change didn't actually work, because I had HTTPS Strict-Transport-Security enabled on the old site and it turns out GitHub Pages doesn't support SSL for custom domains, at all. I kind of assumed that in mid-2017, a year and a half into Let's Encrypt's lifetime, GitHub would have their act together w.r.t. SSL, but I guess not. In lieu of that, I just signed up for CloudFlare's free service, which can wrap insecure sites in SSL - good enough for now. It may take up to 24 hours for the nameservers to propagate; P. Scholasticus, if you want you can revert the custom domain setting on GitHub for that long, to ensure people don't get redirected to a broken URL (although it works for me already). The lists (and list web interface) shouldn't experience problems. Don't worry, I set the firewall level to minimum and whitelisted Tor, so there shouldn't be any CAPTCHA prompts.
