title: IE CORS - Access-Control-Allow-Headers error even though headers are specified
body: <p>I'm currently submitting an AJAX request on a web page to an API endpoint which works in Chrome and Firefox but not in IE.</p>
  
  <p>The error message I'm getting in IE's dev tools is:</p>
  
  <pre><code>SEC7123: Request header x-custom-header was not present in the Access-Control-Allow-Headers list.
  SCRIPT7002: XMLHttpRequest: Network Error 0x80070005, Access is denied.
  </code></pre>
  
  <p><br/>
  Looking at the pre-flight OPTIONS request, here are some of the headers:</p>
  
  <pre><code>Origin: http://www.example.org
  Access-Control-Request-Headers: content-type, accept, x-custom-header
  Access-Control-Request-Method: GET
  </code></pre>
  
  <p>The response of the pre-flight shows this:</p>
  
  <pre><code>Access-Control-Allow-Headers: content-type, x-custom-header
  Access-Control-Allow-Methods: GET, POST, PUT, OPTIONS
  Access-Control-Allow-Origin: *
  </code></pre>
  
  <p><br/>
  After this happens, the AJAX request isn't executed. 
  It looks like IE cannot see that the header was returned in the response of the pre-flight request.</p>
  
  <p><br/>
  Any help would be greatly appreciated and if you need more information, please ask.</p>
  
  <p>Thanks,
  James</p>