Proxied url - form submit loses post request


I have a CF proxied url, with a form page using POST method. When I submit the form, it is sent as a post request, but hits CF, and CF redirects back to my server as a GET request with a 301.

Is there a configuration setting in CF I have not set yet? I would not want to set the url to DNS only as that would cancel the benefits of using CF in the first place.

Any ideas please?

Thank you.