protected function _send($request)
    {
        if (!is_resource($this->_socket)) {
            /**
             * @see Zend_Mail_Protocol_Exception
             */
            // require_once 'Zend/Mail/Protocol/Exception.php';
            throw new Zend_Mail_Protocol_Exception('No connection has been established to ' . $this->_host);
        }

        $this->_request = $request;

        $result = fwrite($this->_socket, $request . self::EOL);

        // Save request to internal log
        $this->_addLog($request . self::EOL);

        if ($result === false) {
            /**
             * @see Zend_Mail_Protocol_Exception
             */
            // require_once 'Zend/Mail/Protocol/Exception.php';
            throw new Zend_Mail_Protocol_Exception('Could not send request to ' . $this->_host);
        }

        return $result;
    }