refer owa(exchange) 2013 via a iframe in sharepoint 2013

Refused to display 'https://cas.temp.local/owa/' in a frame because it set 'X-Frame-Options' to 'SAMEORIGIN'.

create a file named a.cs under C:\Program Files\Microsoft\Exchange Server\V15\FrontEnd\HttpProxy\owa\app_code

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Security;
using System.Security.Principal;

namespace ZY
{
    public class M1 : IHttpModule
    {

        public void Dispose()
        {

        }

        public void Init(HttpApplication application)
        {
        application.PreSendRequestHeaders += new EventHandler(application_PreSendRequestHeaders);

        }
        


        void application_PreSendRequestHeaders(object sender, EventArgs e)
        {
            HttpApplication application = (HttpApplication)sender;
            application.Context.Response.Headers.Set("X-Frame-Options","");
        application.Context.Response.Headers.Remove("X-Frame-Options");
        }

  



    }
}

add a line to web.config(C:\Program Files\Microsoft\Exchange Server\V15\FrontEnd\HttpProxy\owa)

between 

<system.webServer>
<serverRuntime uploadReadAheadSize="0" />
<modules>

<add name="zy" type="ZY.M1" />

</modules>

close web browser ,clear cache and cookies

The OWA 2013 now can display with a iframe under a differetn subdomain