I got this error when a user restored a large amount of email from his archive. It would retry every 5 minutes and the error would occur again. The EV server and the target Exchange server are located across a WAN link. Based on an earlier suggestion in the discussion I went ahead and restarted the archiving task. That seems to have done the trick. I am watching my MSMQ (r2 and r) drop as I type this email and the error has not come back.