This article was previously published under Q245273
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Important This article contains information about how to modify the registry. Make sure to back up the registry before you modify it. Make sure that you know how to restore the registry if a problem occurs. For more information about how to back up, restore, and modify the registry, click the following article number to view the article in the Microsoft Knowledge Base:
256986 Description of the Microsoft Windows registry
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:
There are no more endpoints available from the endpoint mapper.
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:
Microsoft Outlook Web Access 5.5, Microsoft Outlook Web Access 5.5 SP 1, Microsoft Exchange Server 5.5 Service Pack 2, Microsoft Exchange Server 5.5 Service Pack 3, Microsoft Exchange Server 5.5 Standard Edition