We upgraded to exchange 2010 from exchange 2003. About 95% of out users use outlook 2003. The issue we are having is when we try to move or delete emails rather one at a time or several at once, there is a delay. The message will still show in the mailbox folder after you delete or move the message and will continue to show there until you select a different folder or close out of outlook and open it back up. One change that I made was checking the check box for Encrypt data between Microsoft Office Outlook and Microsoft Exchange Server under exchange server settings\ security Tab. Is there anything else thats needs checked or unchecked?