I'm doing a POST request to https://api.stackexchange.com/2.2/users/<id>/inbox to get the users' inbox items. However I'm getting a 400 error on the request, and a JSON body saying it was a 404 error "this method cannot be called this way" and "error_name: no method".

I've form encoded the parameters, and set the content-type to form-urlencoded.

Here's the request in fiddler: