title: Outlook, best way to store variable in an appointment
body: <p>Working on an Outlook Add-In, I need to store a variable inside an appointment to ensure that the recipients can read it.
   So far, I used UserProperty and RTF bookmarks. Both are fine until the invitation crosses the border of the organisation (leave my exchange domain). When it happens, userproperties and RTF bookmarks seem to be removed. Has anyone find a reliable way to do this? I want to avoid ugly hack such as including the variable in small fonts inside the body.</p>
  
  <ul>
  <li>Option 1: Maintain user property => Not possible </li>
  <li>Option 2: Maintain clean RTF</li>
  </ul>
  
  <p>The RTF seems to be converted in a HTML compatible RTF and some tags are lost. The one that I am particulary interested is the following:</p>
  
  <p>Original RTF:</p>
  
  <pre><code>{\\field{\\*\\fldinst{\\ltrch\\f1\\fs22\\cf1\\ulnone\\ulc1 HYPERLINK 
  {\\plain\\ltrch\\f0\\fs24\\ltrch\\f1\\fs22\\cf1\\ulnone\\ulc1 https://www.google.com \\\\o MYLINKNAME}}
  </code></pre>
  
  <p>Converted RTF:</p>
  
  <pre><code>{\\field{\\*\\fldinst{HYPERLINK \"https://www.google.com\"}}
  </code></pre>
  
  <p>The link title property is removed which prevents to retrieve it on the recipient side.</p>