title: Outlook Addin - How can I set “High Importance” on email sent using C# in VSTO
body: <p>I want to know how do I set the headers of email on click on checkboxes. I have created required checkboxes in FormRegion.</p>
  
  <p>Example: 
  I have checkbox named HighImportance, on click of that I want to change the email header.
  I tried this, but it doesn't work:</p>
  
  <pre><code>private void checkBox2_CheckedChanged(object sender, EventArgs e)
  {
      this.OutlookItem.Importance = 2;
  }
  </code></pre>