How to configure OWA to connect to Exchange through a firewall

This article describes how to set up Microsoft Outlook Web Access (OWA) to connect to Microsoft Exchange Server through a firewall. This configuration assumes that there is a firewall between OWA and the Exchange Server computer. There are three ports that need to be opened on the firewall in this configuration. On the Exchange Server computer, two ports need to be statically mapped. To do this, the ports must be opened by editing the registry.

Note The third port, port 135, must be opened on the firewall.

Follow the steps in this section to statically map the two ports on the Exchange Server computer. The Exchange Server computer that OWA points to must have these ports mapped.

Note One port must be mapped for the information store, and one port must be mapped for the directory.

Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:

1. Start Registry Editor (Regedt32.exe).
2. Locate the following key in the registry:
   HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\MSExchangeDS\Parameters
3. Add the following entry for the Microsoft Exchange Directory service:
   Entry: TCP/IP port
   Type: REG_DWORD
   Data: port number to assign
   Note We recommend that you assign ports from the 5000 to 65535 (decimal) range.
   
   For example:
   "TCP/IP Port"=dword:00001388(5000)
4. Locate the following key in the registry:
   HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\MSExchangeIS\ParametersSystem
5. Add the following entry for the Exchange Server information store:
   Entry: TCP/IP port
   Type: REG_DWORD
   Data: port number to assign
   Note We recommend that you assign ports from the 5000 to 65535 (decimal) range.
   
   For example:
   "TCP/IP Port"=dword:00001389(5001)
6. Quit Registry Editor.
7. Restart your computer for the changes to take effect.
8. On the firewall, open the ports that you assigned to the directory, the information store, and port 135 for the endpoint mapper.
   
   Note For the Exchange Server to communicate back through the firewall to the OWA server it is also necessary to have the ephemeral ports 1024 through 65535 configured for outbound communications from the Exchange server to the OWA server. Although you can specify what ports Exchange listens on for RPC traffic, you can not specify what RPC ports the OWA application uses for RPC communications.

Note The OWA server must also be a member of the domain where the mailboxes reside. For additional information about how to configure that access, click the following article number to view the article in the Microsoft Knowledge Base: