public function sendByMail($to, $subject, $body, $cc = null)
    {
        $this->setPostFields($body);

        $this->performRequest(rawurlencode($this->getRecordID()).'/odeslani-dokladu?to='.$to.'&subject='.urlencode($subject).'&cc='.$cc
            , 'PUT', 'xml');

        return $this->lastResponseCode == 200;
    }