Reinstall RPC/HTTP Proxy in SBS 2008

This is generally if you are experiencing problems with the Outlook
Anywhere feature of Exchange - typically you get Exchange Server is down
type errors after authentication.

Disable Outlook Anywhere in EMC.

We are going to have to remove TS Gateway too - as it depends on the RPC
Proxy feature.

Backup the TS Gateway config then remove RPC Proxy feature - it will advise
that TS Gateway will need to be removed too.

Reboot server and uninstall will continue and complete.

Before re-installing the RPC Proxy and TS Gateway features add the
following registry key:
HKLM\SOFTWARE\MICROSOFT\RPC\RpcProxy
Under this key, create a new string value called "Website" and specify "SBS
Web
Applications" for the data.

Re-install RPC Proxy feature and after that install TS Gateway role.
Restore the TS Gateway configuration after installation.

Enable Outlook Anywhere in EMC. Wait around 15 minutes.

At this point you can restart the server to get things going - or restart
IIS and make sure all the Application Pools are running.

Outlook Anywhere should now be working.

Source URL:
http://microsofttoolbox.com/2009/12/how-to-reinstall-the-rpchttp-proxy-feature-in-sbs-2008/