In this code ExchangeConnector.java : 

catch (ServiceRequestException e)
        {
            Throwable cause = e.getCause();
            ExceptionType type = _getExceptionType(cause);
            if (type == ExceptionType.UNKNOWN)
            {
                return false;
            }

I'd like to have the error in the log, for example the cause that is in this case :
"microsoft.exchange.webservices.data.core.exception.service.remote.ServiceResponseException: Le nom principal d'emprunt d'identité n'est pas valide."

I lost a lot of time adding debug thru the VPN for a basic error!