title: How can I access a MailItem after it has been sent?
body: <p>From my WPF app I create and display a <code>MailItem</code> like following:</p>
  
  <pre><code>using Microsoft.Office.Interop.Outlook;
  
  Application outlook = new Application();
  NameSpace ns = outlook.GetNamespace("MAPI");
  MailItem mailItem = outlook.CreateItem(OlItemType.olMailItem);
  mailItem.Display(false);
  string lastEntryId = mailItem.EntryID; // remember EntryId
  </code></pre>
  
  <p>The user can now compose and send the mail.</p>
  
  <p>After the user did send the mail he confirms the sending in my app. My app then should save the mail in file system. My approach was to "remember" the <code>MailItem.EntryID</code> to use it after sending.</p>
  
  <pre><code>// ... lastEntryId is null therefore this code doesn't work
  MailItem mailItem = ns.GetItemFromID(lastEntryId);
  string fileName = GetValidFileName(item.Subject) + ".msg";
  string file = Path.Combine(GetSaveDirectory(), fileName);
  item.SaveAs(file);
  </code></pre>
  
  <p>But <code>lastEntryId</code> is <code>null</code> before sending therefore I cannot use it.</p>
  
  <p>Question is: how can I access the MailItem after it has been sent?</p>