One of our partners has exposed a web service from MS Dynamics NAV and is receiving the below error message when calling the service: System.Net.WebException: The request failed with HTTP status 401: Unauthorized. I have advised that this is not a Mendix error and security permissions need to be set on the MS side, however, he is saying he was able to use SOAP UI to call the web service (after changing the web service to use NTLM authentication), but it prompted for a login. I have advised that he would need to enter credentials in the request header, or integrate the Single Sign On module from the app store into his application. Is this the correct approach? Or would we have to use custom Java? Not sure if this link might provide some clarity: link text