This article explains the steps to change the OWA 2010 timeout values. When a user selects “public computer” in the OWA session, the timeout is 15 minutes by default and 8 hours if “private computer” is selected. He wanted to change the public timeout to be 8 hours as well. Though it is not recommended to have long timeouts for public sessions, below are the steps.
To make any changes to the OWA 2010 timeout (public or private), it is a registry edit on the CAS server. If you have more than one CAS, the change has to be made on all CAS servers.
Launch registry edit and navigate to the following location. HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesMSExchange OWA
Change the DWORD “PublicTimeout” / “PrivateTimeout” and put the required value in minutes. If the DWORD doesn’t exist, create them. My example shows the timeout value to be 480 (minutes), which is 8 hours.
Exchange Forms-Based Authentication service has to be restarted for the changes to take effect.