title: Outlook 2007 Addin Locking Outlook Accessing a deleted Exchange User
body: <p>I have an Outlook 2007 add-in that adds information to calendar items.  I'm running into a problem where if an old Calendar Invite is opened containing Exchange users that are no longer valid, Outlook hangs for around 90 seconds trying to lookup the contact. (Outlook is running in Cached Mode in this case)</p>
  
  <p>I'm trying to figure out if there's a way to access an Exchange user's email asynchronously, or to detect that the user is removed, and simply skip it.  Basically, anything to stop the UI from hanging for a whole minute and a half.</p>
  
  <pre><code>AddressEntry ae = appointmentItem.Recipients[0];
  ExchangeUser eu = ae.GetExchangeUser();//hangs here if user is not in cached address book
  </code></pre>