

I’m using Torsocks 2.3.0 and DiG 9.20.1
It could be the exit node that you’re using perhaps? Maybe you could try specifying a different exit node and trying again. Also check exit node policies to make sure DNS is allowed, although as your problem only seems to be with MX records then that might not be the cause.
Thanks for the detailed write-up, I always “enjoy” reading postmortem reports with detail like these. I say “enjoy” as I enjoy reading about it, but I don’t enjoy thinking about the stress it must have caused. Good job in getting it all sorted!