Working with  my Exchange 2012 Hybrid configuration I into the following error:

ERROR : Subtask NeedsConfiguration execution failed: Configure MRS Proxy Settings

Execution of the Get-WebServicesVirtualDirectory cmdlet has thrown an exception. This may indicate invalid parameters in your hybrid configuration settings.

The task wasn’t able to connect to IIS on the server ‘exchange’. Make sure that the server exists and can be reached from this computer: The RPC server is unavailable.

This is because I did not properly remove the retired exchange servers form Active Directory during past migrations to Exchange 2013.

To remove these objects to continue with your Hybrid configuration task do the following:

  1. Launch the run dialog (Windows Key + R)
  2. Type in the command “adsiedit.msc” and press OK
  3. In the drop down menu select “Configuration”
  4. Expand “CN=Configuration [domain]\CN=Services\CN=Microsoft Exchange\CN=[organization]\CN=Administrative Groups\CN=Servers”
  5. Right click on the dead server and “Delete”
  6. Navigate to ”CN=Configuration [domain]\CN=Services\CN=Microsoft Exchange\CN=[organization]\CN=Administrative Groups\CN=Databases”
  7. Right click on each dead database and “Delete”

Step 1-5 will get you past the Hybrid error, but you might as well cleanup while your here.