Though it’s a good security feature to timeout users by default, one can have some issues with people using just OWA to read their mail having to enter the password every 5 minutes. So here’s how to increase the timeout.

By default the Public timeout is 15 minutes where as the Private timeout is of 8 hours.

If you would like to change these simply do the following.

Open registry editor
Navigate to HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesMSExchange OWA
Create new DWORD named PrivateTimeout
Create new DWORD named PublicTimeout
Now, enter the decimal value in the DWORDs created as required.

Note: The DWORDs entries are in minutes