8:50 and already a rough morning

I got a call this morning while driving into work that the domain we receive the most mail on is not getting email. Naturally since I recently requested some changes in the way we receive mail that was blamed first.
It turns out they were right, in a way. I had requested that we update DNS so we no longer have a wildcard MX record. With a wild card mx record, you could address mail to anyserver.example.com (obviously not our real domain) and it would be delivered to our MTA. Since this causes us to process a lot of unnecessary email I thought we should remove that.
We use split DNS and run our external DNS through our ISP. When AT&T/SBC performed the update instead of removing the wildcard mx record, they removed example.com.
So we’re getting no email addressed @example.com. The negative response cache TTL is 2 hours. So even after we get SBC to fix the record, we may not get email for a while.
At least this is a reminder that people should be using our new domain name instead of the old example.com.
If we had been monitoring our external MX records, we would have seen them go away and possibly gotten it fixed before most peoples cached response expired.