Random emails from one user cannot be opened in Outlook 2007 by other internal users. The same email sent to external email addresses opens fine. The user also cannot open the copy of the message automatically saved in the Sent Mail folder. The error message Outlook shows is "Cannot open this item. Unknown error." I did an offline defrag (eseutil /d) once, and the problem went away, but it returned. I have made sure Trend Micro is not scanning the Exchange database. Subsequent offline defrags have not helped. Any ideas? Thanks.