I just spent the last 1 1/2 hours trying to figure out where all of our emails where going. Not in the queue, no errors, troubleshooter didn't show anything unusual.
Then went to mxtoolbox.com and smtp tests dropped the connection every time. Noticed this posting and figured I'd better look at KAV 8 for exchange.
Tried deleting the local host... nothing.... uninstalled, reboot and the last 1 1/2 hours of email is now flowing through.
So, let me know if you hear of a patch. For now, I'll have to leave it as is.