public function exists($email)
    {
        $path = $this->getUrl($email, null, null, '404');

        if (!$sock = @fsockopen('gravatar.com', 80, $errorNo, $error)) {
            return;
        }

        fwrite($sock, 'HEAD '.$path." HTTP/1.0\r\n\r\n");
        $header = fgets($sock, 128);
        fclose($sock);

        return strpos($header, '404') ? false : true;
    }