I am experiencing an issue with Exchange 2010 and undelivered email. I have a single Exchange 2010 server with two mounted databases. I have seen a large amount of growth over the last few weeks due to business operations. A new monitoring system had recently been deployed but was not configured properly. It caused the drive with my mounted databases to almost fill up. Users quit receiving email from external sources. The problem was not noticed or reported for about 8-10 hours after it occurred. The exchange server is running on a VM so the additional space was added to the server and it was rebooted. Before rebooting I verified there were no messages in the queues awaiting delivery. I assumed any undelivered messages would be resent by the orginating server once the issue was corrected. That has not happened so I am basically looking at 8-10 hours of lost email. Does anyone have any suggestions or can someone shed some light on this one for me?