protected function _sendMail()
    {
        $file = $this->_path . DIRECTORY_SEPARATOR . call_user_func($this->_callback, $this);

        if (!is_writable(dirname($file))) {
            // require_once 'Zend/Mail/Transport/Exception.php';
            throw new Zend_Mail_Transport_Exception(sprintf(
                'Target directory "%s" does not exist or is not writable',
                dirname($file)
            ));
        }

        $email = $this->header . $this->EOL . $this->body;

        if (!file_put_contents($file, $email)) {
            // require_once 'Zend/Mail/Transport/Exception.php';
            throw new Zend_Mail_Transport_Exception('Unable to send mail');
        }
    }