This MSITemp folder is a hidden folder located in some of our users mail boxes that appears to hold older email. Newer clients and the OWA cannot see it nor does it show up when looking at folder sizes from within them. It can only be seen from an Outlook 2000 client. The affected mail boxes start running out of space because this folder is being counted as part of their mailbox size by the server. Exchange 2007 servers Outlook 2003, 2007, 2000 Anyone have any idea what this folder is and why it is hidden? Is there a way to view hidden folders in newer outlook clients in order for our users to manage it? Is there something we can be doing, or should have done, to make it so that the folder is not created or utilized? Thanks in advance.

This usually happens if users have evaluated any third party application which uses outlook and kept some stale entries of their usage or any third party add-ins for outlook is used by user. Check below similar thread, you can make it visible thorough MFCMapi, check content and delete it if not required. http://social.technet.microsoft.com/Forums/en-US/exchangesvrgeneral/thread/9c642296-5838-4f35-8cbb-22b01b4e8fce Amit Tank | MVP - Exchange | MCITP:EMA MCSA:M | http://ExchangeShare.WordPress.com