snipe-it/app/Notifications/MailTest.php

<?php

namespace App\Notifications;

use Illuminate\Bus\Queueable;
use Illuminate\Notifications\Messages\MailMessage;
use Illuminate\Notifications\Notification;
use Symfony\Component\Mime\Email;

#[AllowDynamicProperties]
class MailTest extends Notification
{
    use Queueable;

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

    /**
     * Get the notification's delivery channels.
     *
     * @return array
     */
    public function via()
    {
        return ['mail'];
    }

    /**
     * Get the mail representation of the notification.
     *
     * @return \Illuminate\Notifications\Messages\MailMessage
     */
    public function toMail()
    {
        return (new MailMessage)
        ->subject('👋 '.trans('mail.test_email'))
        ->markdown('notifications.Test')
        ->withSymfonyMessage(function (Email $message) {
            $message->getHeaders()->addTextHeader(
                'X-System-Sender', 'Snipe-IT'
            );
        });
    }
}