Log emails as *.eml in Laravel Mailer

EventServiceProvider.php

<?php

namespace App\Providers;

use App\Listeners\LogSentMessage;
use Illuminate\Foundation\Support\Providers\EventServiceProvider as ServiceProvider;
use Illuminate\Mail\Events\MessageSent;

class EventServiceProvider extends ServiceProvider
{
    /**
     * The event listener mappings for the application.
     *
     * @var array
     */
    protected $listen = [
        MessageSent::class => [
            LogSentMessage::class,
        ],
    ];
}

filesystems.php

<?php

return [
    // ...
    'disks' => [
        // ...
        'emails' => [
            'driver'     => 'local',
            'root'       => storage_path('logs/emails'),
        ],

LogSentMessage.php

<?php

namespace App\Listeners;

use Illuminate\Mail\Events\MessageSent;
use Illuminate\Support\Facades\Storage;
use Illuminate\Support\Str;

class LogSentMessage
{
    public function handle(MessageSent $event)
    {
        $messageId = $event->data['__laravel_notification_id'] ?? Str::uuid();
        Storage::disk('emails')->put(
            sprintf('%s_%s.eml', now()->format('YmdHis'), $messageId),
            $event->message->toString()
        );
    }
}