Exchange 2010 RPC/HTTP Proxy and Autolook Anywhere

Sometimes Outlook Anywhere doesn't function correctly.  I always start by using "Exchange Analyzer".  Recently using this I found an issue where IIS was returning a 500 Authentication error.  Here's what worked for me. 

Connect to the Exchange Client Acces Server

Ensure the RPC over HTTPs feature is installed and that Outlook Anywhere is enabled. 

Browse to the follwoing location: 

C:\Windows\System32\RpcProxy 

Copy the web.config file to web.config.backup.

Open web.config in Notepad. 

Replace the following section: 

<system.webServer> 

<modules> 

</modules> 

</system.webServer> 

With: 

<system.webServer> 

<validation validateIntegratedModeConfiguration="false" /> 

</system.webServer> 

Save the file and restart iis via a command prompt: IISRESET 

You should now be good to go!