XWEB: OWA Setup Error Message: There Are No More Endpoints Available from the Endpoint Mapper

When you attempt to install Outlook Web Access (OWA) with a firewall between the Microsoft Internet Information Server (IIS)/OWA server and the Exchange Server computer, you receive the following error message:

During the installation of OWA, the Exchange Server installation program needs to bind to the system attendant on the Exchange Server computer. If the port for the system attendant is being blocked by the firewall, the installation does not work.

Warning Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method. These problems might require that you reinstall your operating system. Microsoft cannot guarantee that these problems can be solved. Modify the registry at your own risk.
To resolve this problem, statically map the system attendant port on the Exchange Server computer, and then open that port on the firewall. This allows the installation program to bind to the system attendant during installation. To do so requires you to restart the Exchange Server services. To statically map the system attendant port on the Exchange Server computer:

1. Start Registry Editor (Regedt32.exe).
2. Locate the following registry key:
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeSA\Parameters
3. Add the registry value, TCP/IP port, as a DWORD value, and specify the port to be used. Set the RADIX to decimal when you enter the value.
   
   NOTE: The DWORD value must be in decimal. The port must be above 1024, preferably above 5000.
4. Quit Registry Editor.

You must also statically map the information store and the directory service, and open those ports on the firewall.

For more information, click the following article number to view the article in the Microsoft Knowledge Base: