protected function getHtmlBody()
    {
        $charset    = $this->isUtf8($this->body['text/html']) ? 'utf-8' : 'US-ASCII';
        $html       = str_replace("\r", '', trim($this->body['text/html']));

        $encoded = explode("\n", $this->quotedPrintableEncode($html));
        $body   = array();
        $body[] = 'Content-Type: text/html; charset='.$charset;
        $body[] = 'Content-Transfer-Encoding: quoted-printable'."\n";

        foreach ($encoded as $line) {
            $body[] = $line;
        }

        $body[] = null;
        $body[] = null;

        return $body;
    }