code: protected void actuallySend(SMailPostingMessage message) throws MessagingException {
          final Transport transport = prepareTransport();
          final MimeMessage mimeMessage = message.getMimeMessage();
          transport.connect(); // authenticated by session's authenticator
          transport.sendMessage(mimeMessage, mimeMessage.getAllRecipients());
          message.acceptSentTransport(transport); // keep e.g. last return code
      }
docs: --------