We had a DOS attack on our servers in Chicago. We blocked this attack. During the period of the attack, some services automatically failed over to the LAX datacenter as our system is designed to do. The clusters in the LAX datacenter processed all the email, though some fell slightly behind in processing under the increased load. Instead of greatly delaying messages, some messages with attachments were passed through with only the most basic, standard virus and spam filtering, rather than going through our usual full suite of checks. These messages were marked "UNCHECKED" in the headers.
The issue has been repaired, and we don't anticipate any further problems like this to arise. We are considering other ways of marking any future messages that go through with the minimal filtering with something other than the "UNCHECKED" subject tag, since it is, indeed, misleading, and is causing unnecessary but understandable concern from customers.
Mailroute Support Team