title: Outlook web add-in activation rules in manifest
body: <p>I am having trouble activating my add-in when a message is encrypted or signed.
  It works fine on regular messages, but with encrypted or signed messages the button is just grayed out.  </p>
  
  <p>I have tried this without any luck:</p>
  
  <pre class="lang-xml prettyprint-override"><code>&lt;Rule xsi:type="ItemIs" ItemType="Message" FormType="Read" ItemClass="IPM.Note.Secure" IncludeSubClasses="true" /&gt;
  &lt;Rule xsi:type="ItemIs" ItemType="Message" FormType="Read" ItemClass="IPM.Note.Secure.Sign" IncludeSubClasses="true" /&gt;
  </code></pre>