"ERROR: Server was unable to process request. ---> Unable to generate a temporary class (result=1)." error CS2001: Source file 'C:\Windows\TEMP\filename.0.cs' could not be found (4297475)

Free/Busy requests do not work from Exchange to Domino and the following error is seen in the Outlook 2010 logs , when debug logging is enabled or in the Exchange Server Event Viewer:

"Server was unable to process request. ---> Unable to generate a temporary class (result=1).
error CS2001: Source file 'C:\Windows\TEMP\filename.0.cs' could not be found ".

In the Coexistence Manager For Notes Server , follow these steps:

1. Go to 'C:\Windows\TEMP\' folder
2. Right Click on it
3. Go to Properties
4. Click the Security tab
5. Click Advanced
6. If the IIS group group is not listed, Add the group.  Once added, or if it was already listed, set the permissions to at least:  

List folder / read data   

        7. If the Users group is not listed, Add the group.  Once added, or if it was already listed, set the permissions to at least:

        8.  Apply all changes and click OK until all dialogs are closed

NOTE: Make sure those permissions are applied to that folder, subfolder and files.