Set User Inactivity Limit
If Outlook Web Access client computers connect to their Exchange server and are inactive for a period of time, they are still using resources on the server. In order to keep resources free, you may want to set a limit on the number of minutes a user can be inactive before Outlook Web Access will end the user context. If a user returns to Outlook Web Access after the user context has timed out, the user will not have to enter user name and password again.
Note When the user returns to their computer after an extended period and connects to Outlook Web Access, the browser will resend the cached credentials to the Exchange server without prompting the user.
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 set a limit on user inactivity: