private function getCapabilities($ehloResponse)
    {
        $capabilities = [];
        $ehloResponse = trim($ehloResponse);
        $lines = explode("\r\n", $ehloResponse);
        array_shift($lines);
        foreach ($lines as $line) {
            if (preg_match('/^[0-9]{3}[ -]([A-Z0-9-]+)((?:[ =].*)?)$/Di', $line, $matches)) {
                $keyword = strtoupper($matches[1]);
                $paramStr = strtoupper(ltrim($matches[2], ' ='));
                $params = !empty($paramStr) ? explode(' ', $paramStr) : [];
                $capabilities[$keyword] = $params;
            }
        }

        return $capabilities;
    }