My Exchange server is crashing on an fairly regular basis. When I look at the Event viewer I find Application errors that read like the fiollowing; A non-delivery report with a status code of 4.4.7 was generated for recipient rfc822;email@example.com (Message-ID <firstname.lastname@example.org>). Cause: Message in queue has expired. The sending server tried to relay or deliver the message but the action could not be completed before the message expired. Solution: This message usually indicates a problem on the receiving server. Check the validity of recipients address and verify that the receiving server is configured to receive messages correctly. Resending the message will place it again in the queue, if the receiving server is up, message delivery will succeed. When I look at the System errors I find the following; An I/O operation initiated by the Registry failed unrecoverably. The Registry could not read in, or write out, or flush, one of the files that contain the system's image of the Registry. The driver failed to allocate memory. This started last Friday. I am running McAfee Virus scan to look for issues but Is there something else I should be looking at? The only thing different with the Exchange 2003 server is I upgraded my Veritas Backup Exec from Version 9.0 to 9.1 and installed Remote Agent on a new server that I want to back up from the Exchange server.