title: System.Net.SmtpClient SendAsync() method's internal implementation
body: <p>I wanted to know the internal implementation of System.Net.SmtpClient's SendAsync() method's internal implementation, If it uses the ThreadPool's Thread or only uses the current synchronization context??</p>
  
  <p>In <a href="https://stackoverflow.com/questions/6173279/difference-between-smtpclient-send-and-smtpclient-sendasync/#6173314">this</a> answer it is said that it uses the threadpool's thread but when I looked at System.dll's decompiled code it didn't had any Threadpool used(or maybe I didn't understand the code).</p>
  
  <p>I just wanted to know this for my implementation of sending bulk emails where I was stuck between to use SendAsync method or just use the Send() method in ThreadPool.QueueUserWorkItem...</p>