Try again later tonight.
I run the primary mail server for my domain. I mistyped the name of said server in the DNS file.
Fortunately, I have a backup mail server provided by Speakeasy.
Unfortunately, their backup mail server is misconfigured and is rejecting all mail for me.
I've contacted them about it, and also corrected the typo in the DNS file, so one way or another, I should be getting mail again soon. It's a race between Speakeasy tech support and GANDI DNS propagation. Bets?