public function getAttachment($attachmentName)
    {
        if ($attachmentName == '')
            throw new Exception('Attachment Name not specified');

        //build URI
        $strURI = Product::$baseProductUri . '/email/' . $this->getFileName() . '/attachments/' . $attachmentName;

        //sign URI
        $signedURI = Utils::sign($strURI);

        $responseStream = Utils::processCommand($signedURI, 'GET', '', '');

        $v_output = Utils::validateOutput($responseStream);

        if ($v_output === '') {
            $outputFilename = $attachmentName;
            Utils::saveFile($responseStream, AsposeApp::$outPutLocation . $outputFilename);
            return $outputFilename;
        } else {
            return $v_output;
        }
    }