function settingsTestSmtpConnection()
{
  // Create a new SMTP instance
  $smtp = new SMTP;
  $smtp->do_debug = SMTP::DEBUG_CONNECTION;
  $smtp->Debugoutput = 'error_log';
  try
  {
    // Connect to the SMTP server.
    $server = getSetting('contact_smtp_server');
    $port = getSetting('contact_smtp_port');
    if (!$smtp->connect($server, $port))
    {
      throw new Exception('Connection failed. Check server and port number are correct.');
    }

    // Say Hello.
    if (!$smtp->hello(gethostname()))
    {
      throw new Exception('Connection failed. Check server and port. (EHLO failed): ' . $smtp->getError()['error']);
    }

    //Get the list of ESMTP services the server offers
    $e = $smtp->getServerExtList();

    // If server can do TLS encryption, use it
    if (array_key_exists('STARTTLS', $e))
    {
      $tlsok = $smtp->startTLS();
      if (!$tlsok)
      {
        throw new Exception('Failed to start encryption: ' . $smtp->getError()['error']);
      }

      // Repeat EHLO after STARTTLS
      if (!$smtp->hello(gethostname()))
      {
        throw new Exception('Connection failed. Check server and port. (EHLO (2) failed): ' . $smtp->getError()['error']);
      }

      // Get new capabilities list, which will usually now include AUTH if it didn't before
      $e = $smtp->getServerExtList();
    }

    // Check authentication.
    if (getSetting('contact_smtp_authenticate'))
    {
      $username = getSetting('contact_smtp_user');
      $encrypted = getSetting('contact_smtp_password_encrypted');
      $iv = getSetting('contact_smtp_password_iv');
      $password = cryptDecrypt($encrypted, $iv);

      if ($smtp->authenticate($username, $password))
      {
        $message = 'Connected successfully!';
      }
      else
      {
        throw new Exception('Authentication failed. Check username, password, and authentication method are correct. ' . $smtp->getError()['error']);
      }
    }
    else
    {
      if (array_key_exists('AUTH', $e))
      {
        $message = 'Connected successfully without authentication. However authentication may be necessary for this server. It is recommended to check authentication and test again.';
      }
      else
      {
        $message = 'Connected successfully without authentication!';
      }
    }
  }
  catch (Exception $e)
  {
    $message = $e->getMessage();
  }

  // Whatever happened, close the connection.
  $smtp->quit(true);
  return $message;
}