--On Thursday, April 30, 2020 6:08 PM -0500 Chris Adams linux@cmadams.net wrote:
From your traceroutes, it kind of looks like it's possible that it's something on your gateway (but I'm not really sure). Do you have any IPv6 firewall running there?
I dropped the firewall just to make sure it wasn't the issue. My connections to Linode eventually started working. Comparison to the traceroute I posted earlier shows a different router just before my server, so I suspect they had a bad router. I still can't connect the other way, towards AT&T. But routing must be working because replies from outbound connections are getting back. I'd file a ticket with AT&T but they still haven't added my account to their ticket system after more than a week of service. So I'm stuck playing tag with the sales consultants.
One other note about mail on v6 - not only do you need to have a valid reverse (with matching forward) DNS record, you probably need to do TLS with a valid cert (Let's Encrypt is free and easy).
Thanks for reminding me. I added an IPv6-only name for testing and for my reverse and need to add that to my certificate.