title: Force Outlook Add-in popup to open with embedded browser
body: <p>I'm seeing an issue with my Outlook Add-in (running in Outlook 2016) where when I open a popup window using <code>window.open</code>, it sometimes opens in the user's default browser (e.g. Chrome) instead of the browser running the add-in (e.g. the IE11 web view embedded in Outlook 2016). This is a problem because it prevents the popup window from communicating with the add-in, which is necessary for clickjacking protection.</p>
  
  <p>Is there a way to force the popup window to be opened in the same browser that is running the add-in, without using the Dialog API? I would like to support requirement set 1.3.</p>