 <p>I know the question is old, but since I found it, others may find it as well. And then, the solution is five years older than this question.</p> <p>The solution is in fact simple and will be found quickly when trying to post this problem at the microsoft forums:</p> <p><a href="http://social.msdn.microsoft.com/Forums/en-US/0403c00e-008d-4eb2-a061-45e60664573e/how-can-i-get-smtp-address-to-an-organizer-with-ews?forum=exchangesvrdevelopment" rel="nofollow">http://social.msdn.microsoft.com/Forums/en-US/0403c00e-008d-4eb2-a061-45e60664573e/how-can-i-get-smtp-address-to-an-organizer-with-ews?forum=exchangesvrdevelopment</a></p> <p>Short summary:</p> <p>The organizer field does not contain an SMTP Address when retrieved with ExchangeService.FindAppointments, but it does if retrieved with ExchangeService.BindToItems or Appointment.Bind.</p>