Impersonate an outgoing call

Hi,

I'm trying to make place a call and use Impersonation on that call. But I get an exception of the type InvalidOperationException with the message "User endpoint or platform does not support impersonization."

I'm using impersonization in a BackToBack scenario in my code, so I guess that means that the Application endpoint is configured correct.

I've been struggling with this for a while now so any help would be greatly appreciated. My best guess is that you cannot use Impersonate on an outgoing call, is this assumption correct?

Here's an excerpt of the code, the Conversation is created earlier.

                try
                {
                    conv.Impersonate("sip:someone@somewhere.com", "tel:+1234", "Me");
                }
                catch (Exception ex)
                {
                    _logger.ErrorFormat("MakeCall: Caught Impersonate exception {0}", ex.Message);
                }


                extAvCall.StateChanged += new EventHandler<CallStateChangedEventArgs>(_lyncEvtHandlers.OnOutgoingAVCallStateChanged);
                extAvCall.BeginEstablish(destUri, callOptions, ar =>
                { 
                    try
                    {
                        CallMessageData callMsgData = extAvCall.EndEstablish(ar);                    }
                    catch (RealTimeException rtex)
		    {
		    ...
		    }

Regards

/Rehan