Using Ajax to submit a form and returning a confirmation page

Question

I am trying to submit a form through an ajax process :

 @using (Ajax.BeginForm("SendEmail", "Form", new AjaxOptions
        {
            UpdateTargetId = "replace",
            InsertionMode = InsertionMode.Replace,
            HttpMethod = "Post",
        }))
        {
         // the form details
        }

the action for this form is defined in the Form controller as:

[HttpPost]
 public ActionResult SendEmail(EnquiryFormViewModel model)
        {
           _sendForm.SendFormByEmail(model.FirstName, model.Surname, model.Email, model.NatureOfEnquiry,model.Message);
            return PartialView("EmailResult", model.FormMetaData);
        }

The route is defined in the global.asax as:

  //Form button
            routes.MapRoute(
                name: "FormButton",
                url: "Form/{action}",
                defaults: new { controller = "Form", action = "SendEmail" }
                ).DataTokens.Add("area", "Core");

The action is supposed to return a partial page that contains some information about the successful submission of the form and thanking the user. However, as soon as the button is clicked, I get a 404 error that Requested URL: /Form/SendEmail is not available. The action method is executed, but I can't get the page that I am supposed to get through the action. How can I fix this?