public function getAutodiscoverRequest()
    {
        if (!empty($this->requestxml)) {
            return $this->requestxml;
        }

        $xml = new \XMLWriter();
        $xml->openMemory();
        $xml->setIndent(true);
        $xml->startDocument('1.0', 'UTF-8');
        $xml->startElementNS(
            null,
            'Autodiscover',
            'http://schemas.microsoft.com/exchange/autodiscover/outlook/requestschema/2006'
        );

        $xml->startElement('Request');
        $xml->writeElement('EMailAddress', $this->email);
        $xml->writeElement(
            'AcceptableResponseSchema',
            'http://schemas.microsoft.com/exchange/autodiscover/outlook/responseschema/2006a'
        );
        $xml->endElement();
        $xml->endElement();

        $this->requestxml = $xml->outputMemory();
        return $this->requestxml;
    }