Engage.so laravel headers setup

AppServiceProvider.php

<?php

namespace App\Providers;

use Illuminate\Support\ServiceProvider;

use Illuminate\Mail\Events\MessageSending;
use Illuminate\Support\Facades\Event;

class AppServiceProvider extends ServiceProvider
{
    /**
     * Register any application services.
     *
     * @return void
     */
    public function register()
    {
        //
    }

    /**
     * Bootstrap any application services.
     *
     * @return void
     */
    public function boot(UrlGenerator $url)
    {
        Event::listen(MessageSending::class, function (MessageSending $event) {
            $event->message->getHeaders()->addTextHeader('X-SES-CONFIGURATION-SET', 'engage_so');
            $event->message->addBcc('mails@ses.engage.so', 'Engage.so');
            
        });
    }

}