How to fix Exchange 2007 RPC over HTTPS/Outlook Anywhere on Windows Server 2008

A small but anoying bug in Microsoft Exchange 2007 in combination with Windows Server 2008, will under certain conditions make Outlook Anywhere (OA) fail no matter how correct your settings are in Exchange 2007.

The Outlook Anywhere error only shows under theese conditions.

  • Any Exchange 2007 version
  • Client Access Server (CAS) and Mailbox Server roles installed on the same server
  • Operating system any version and edition of Windows Server 2008, with RPC Proxy feature installed (required for OA).

The reason for the bug and the fix is very simple…

The error is caused by a combination of the Windows Server 2008 RPC Proxy feature and Windows Server 2008 prefering IPv6 over IPv4 when talking to it self either with the localhost or the servername address. This means that when the CAS role contacts the RPC proxy on the same server, it will use the local ServerName resulting in the IPv6 address of :::1: instead of In it self this should not be a problem, however the RPC Proxy feature is bugged and does not listen on one of the 3 ports used (6001-6002 and 6004) when using the IPv6 address. So the RPC over HTTPS connection will fail.

To resolve the problem all You have to do is make the server use the IPv4 address instead of the IPv6 address when contacting it self.

Resolution #1 (Recommended resolution)
Edit the hosts file to use IPv4 localhost address instead of the IPv6 address :::1:, for the local ServerName and localhost addresses, the hosts file is located in the \Windows\System32\Drivers\etc folder. (Remember to start the editing with Administrator permissions)

Resolution #2
By not placing the CAS and Mailbox roles on the same server, and using IPv4 networking, the connection will go with IPv4 to the Mailbox server with RPC Proxy installed.

Resolution #3 (I would not recommend this solution.)
Use Windows Server 2003 on the Mailbox role, since it does not prefer IPv6 it wont be an issue.

Remember to get Outlook Anywhere working you will need to have the Windows feature RPC Proxy installed.

3 Responses to “How to fix Exchange 2007 RPC over HTTPS/Outlook Anywhere on Windows Server 2008”

  • Sole:

    Just a quick note, this bug can be found in with an error during “Testing NSPI Interface on Exchange Mailbox Server” wich will fail on “Attempting to ping RPC Endpoint 6004 (NSPI Proxy Interface) on server your-server-name”

    If You get this error, make sure to check the rest of this article with how to fix it.

  • This was great. My team and I spent many hours tracking this down, running tests and other efforts. It did save time. i believe if you ensure IPv6 is not enabled when installing Exchange this should not be an issue..

    Thanks for sharing, it is relevant even many years after your post.

  • MC:

    Close to 5 years after the fact…THANK YOU THANK YOU THANK YOU. This bug was preventing us from migrating a mail server.

    Looked everywhere, spent hours and hours, nothing. Finally I came across this.

    Thank you.

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