The HT has a couple of email addresses linked to his mailbox and an important email that was sent last week has not come through to his mailbox even though the logs say it has. My first thought was that it has been deleted by mistake but I checked the HT deleted folder and there's no sign of the missing email. Then I checked the Exchange message tracking logs in EMC and it's listed but when I click details it gives an error saying the delivery report information for this message is no longer available. On other messages of the same age I can get the delivery info so something is not right.

Where could the email have gone?