title: Mail being rejected, but not with error I would expect
body: <p>First the simple mail code:</p>
  
  <pre><code>var objMail = new MailMessage(myEmail, myEmail, "Test Message", "Some message");
  var objNc = new NetworkCredential("complete", "rubbish");
  var objsmtp = new SmtpClient(myExchangeServer") { UseDefaultCredentials = false, Credentials = objNc };
  </code></pre>
  
  <p>I started off with correct credentials and getting this message from exchange:</p>
  
  <blockquote>
    <p>Mailbox unavailable. The server response was: 5.7.1 Message rejected as spam by Content Filtering.</p>
  </blockquote>
  
  <p>Exchange problem I thought, but I then tried with bad credentials (user: complete password: rubbish) and I get the same exception.</p>
  
  <p>I would have expected an authentication error, so I suspect I am specifying the credentials incorrectly?</p>