title: Where are Exchange Web Services: ExtendedPropertyDefinition IDs defined?
body: <p>In researching how to use Exchange Web Services, I see examples like this</p>
  
  <pre><code>Dim PR_DELETED_ON As New ExtendedPropertyDefinition(26255, MapiPropertyType.SystemTime)
  Dim PR_SEARCH_KEY As New ExtendedPropertyDefinition(12299, MapiPropertyType.Binary)
  </code></pre>
  
  <p>That first parameter is an int that represents the property ID.  Can anyone give me a pointer to where those ID numbers are defined? </p>