title: javax.mail: Proof of transmission
body: <p>When I send an e-mail with</p>
  <pre><code>javax.mail.Transport.send(msg);
  </code></pre>
  <p>is the any chance to log the communication with the SMTP server into a file as a proof of transmission? Sometimes customers complain that they don't receive an e-mail, but I don't get any &quot;Throwable&quot; exception when sending the e-mail. So how can I proof, that my program delivered the mail correrctly to the smtp server?</p>