Display Alert Message at Logoff Time
If an Outlook Web Access user walks away from their computer and leaves their web browser open, it is possible for an unauthorized person to use authentication credentials in the browser's cache to access the mailbox. When the WarnOnLogoff registry key is added, users will receive a pop-up warning message whenever they navigate away from Outlook Web Access. The message will notify users that if they close their browser window or go to another Web site without first logging off from Outlook Web Access, their mailbox may be compromised.
Keep in mind that once this registry key is activated, users will also see this message whenver they refresh their browsers (such has by hitting F5 on their keyboards).
Warning Using Registry Editor incorrectly can cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk.
For information about how to edit the registry, view the "Add and Delete Information in the Registry" and "Edit Registry Data" Help topics in Regedt32.exe. Note that you should back up the registry before you edit it, and you should also update your Emergency Repair Disk (ERD).
To enable logoff alert messages: