title: How to implements secure connections (No | SSL | STARTTLS) in SmtpClient to send mail?
body: <p>I use class SmtpClient of namespace System.Net.Mail to send mail:
  I create SmtpClient to send mail:</p>
  
  <pre><code>private static SmtpClient CreateSmtpClient (string host, string user, string password, int port)
          {
              var smtpClient = new SmtpClient (host, port);
              smtpClient.Credentials = new NetworkCredential (user, password);
              return smtpClient;
          }
  </code></pre>
  
  <p>and use it:</p>
  
  <pre><code>var mailMessage = new MailMessage ();
  var smtpClient = CreateSmtpClient (host, user, password, port);
  smtpClient.Send (mailMessage);
  </code></pre>
  
  <p>How to implements secure email transfer when I have 3 option secure connection is: No | STARTTLS | SSL ?
  Many thanks !</p>