public function trySubdomainUnauthenticatedGet()
    {
        $this->reset();
        $url = 'http://autodiscover.' . $this->tld . self::AUTODISCOVER_PATH;
        $ch = curl_init();
        $opts = array(
            CURLOPT_URL                 => $url,
            CURLOPT_HTTPGET             => true,
            CURLOPT_RETURNTRANSFER      => true,
            CURLOPT_TIMEOUT             => 4,
            CURLOPT_CONNECTTIMEOUT      => $this->connection_timeout,
            CURLOPT_FOLLOWLOCATION      => false,
            CURLOPT_HEADER              => false,
            CURLOPT_HEADERFUNCTION      => array($this, 'readHeaders'),
            CURLOPT_HTTP200ALIASES      => array(301, 302),
            CURLOPT_IPRESOLVE           => CURL_IPRESOLVE_V4
        );
        curl_setopt_array($ch, $opts);
        $this->last_response    = curl_exec($ch);
        $this->last_info        = curl_getinfo($ch);
        $this->last_curl_errno  = curl_errno($ch);
        $this->last_curl_error  = curl_error($ch);

        if ($this->last_info['http_code'] == 302
            || $this->last_info['http_code'] == 301) {
            if ($this->tryViaUrl($this->last_response_headers['location'])) {
                return self::AUTODISCOVERED_VIA_UNAUTHENTICATED_GET;
            }
        }

        return false;
    }