Chapter80 writes "At noon today (Eastern Standard Time), the long dead ORDB spam identification system began returning false positives as a way to get sleeping users to remove the ORDB query from their spam filters. The net effect: all mail is blocked on servers still configured to use the ORDB service, which was taken out of commission in December of 2006. So if you're not getting any mail, check your spam filter configuration!"
If it happens once, it's a bug. If it happens twice, it's a feature.
If it happens more than twice, it's a design philosophy.