Outlook invitation from Laravel

InviteMail.php

<?php

namespace App\Mail;

use Illuminate\Bus\Queueable;
use Illuminate\Contracts\Queue\ShouldQueue;
use Illuminate\Mail\Mailable;
use Illuminate\Queue\SerializesModels;
use App\Traits\Monday\Monday;
use Illuminate\Support\Facades\Mail;

class InviteMail extends Mailable implements ShouldQueue
{
    use Queueable, SerializesModels, Monday;

    public $subject;
    private $toAddress;
    private $message;
    private $headers;
    private $fromName;
    private $fromAddress;

    /**
     * Create a new message instance.
     *
     * @return void
     */
    public function __construct() {}

    /**
     * Build the message.
     *
     * @return $this
     */
    public function build()
    {
        $fromName = "From Kumar";
        $fromAddress = "fromKumar@email.com";
        $toName = "To Kumar";
        $toAddress = "toKumar@email.com";
        $subject = "Add your subject here";
        $description = "Add your description here";
        $location = "Vivek's House";

        // Add message
        $mimeBoundary = "----Meeting Booking----" . MD5(TIME());
        $message = "--$mimeBoundary\r\n\n";
        $message .= $description . "\r\n\n";
        $message .= "--$mimeBoundary";

        $this->message = $message;

        $vcal = $this->createEvent($fromName, $fromAddress, $toName, $toAddress, $location, $description);

        $this->sendInvite($vcal, $toAddress, $subject);
    }

    private function createEvent(
        string $fromName,
        string $fromAddress,
        string $toName,
        string $toAddress,
        string $location,
        string $description
    ): string {
        $timeStamp = \Carbon\Carbon::now();

        $meetingDuration = (60 * 60);
        $meetingstamp = $timeStamp->getTimeStamp();
        $dtstart = gmdate('Ymd\THis\Z', $meetingstamp);
        $dtend =  gmdate('Ymd\THis\Z', $meetingstamp + $meetingDuration);
        $uid = date('Ymd') . 'T' . date('His') . '-' . rand();

        $organizer = "Organizer name:" . $fromName;
        $organizerEmail = $fromAddress;

        $vcal = "BEGIN:VCALENDAR\r\n";
        $vcal .= "VERSION:2.0\r\n";
        $vcal .= 'PRODID:-//Microsoft Corporation//Outlook 10.0 MIMEDIR//EN' . "\r\n";
        $vcal .= "METHOD:REQUEST\r\n";
        $vcal .= "BEGIN:VEVENT\r\n";
        $vcal .= "ORGANIZER;CN=\"$organizer" . "\":mailto:$organizerEmail\r\n";
        $vcal .= 'ATTENDEE;CN="' . $toName . '";ROLE=REQ-PARTICIPANT;RSVP=TRUE:MAILTO:' . $toAddress . "\r\n";
        $vcal .= "UID:" . $uid;
        $vcal .= "DTSTAMP:" . date('Ymd') . 'T' . date('His') . "\r\n";
        $vcal .= "DTSTART:$dtstart\r\n";
        $vcal .= "DTEND:$dtend\r\n";
        $vcal .= "LOCATION:$location\r\n";
        $vcal .= "SUMMARY:$description\r\n";
        $vcal .= "DESCRIPTION:$description \r\n";
        $vcal .= "BEGIN:VALARM\r\n";
        $vcal .= "TRIGGER:-PT15M\r\n";
        $vcal .= "ACTION:DISPLAY\r\n";
        $vcal .= "DESCRIPTION:Reminder\r\n";
        $vcal .= "END:VALARM\r\n";
        $vcal .= "END:VEVENT\r\n";
        $vcal .= "END:VCALENDAR\r\n";

        return $vcal;
    }

    private function sendInvite(string $vcal, string $toAddress, string $subject): void
    {
        Mail::raw($this->message, function ($mail) use ($vcal, $toAddress, $subject) {
            $swiftObj = $mail
                ->to($toAddress)
                ->subject($subject)
                ->getSwiftMessage();

            $swiftObj->addPart($vcal, 'text/calendar; method=REQUEST', 'iso-8859-1');
        });
    }
}