The server’s response means that the URL that you are using is not correct. The service is at a different location.
Exactly what Joost says. Mendix doesn't follow redirects, unlike Postman and SoapUI do. This is done on purpose: for security reasons.
You could look up the redirect URL by sending a test message from Postman or SoapUI and use that.
If that is somehow not possible, you could build a error handler, check the error message and retry using the redirected URL.
This was my first guess too, but I checked the URL and it’s correct.
I tested this request with SOAP UI and the URL worked and when typing the URL in the browser I get:
Dear Jost and Johan,
thank you for your fast replies, actually I am getting now my desired response back! There was actually a redirect in SoapUI.