Notifications in queue not send email

I have created a notification with laravel so that when the user submits the contact form he will receive a confirmation email.

I also set my queue driver as a database and performed all the migrations as the documentation says.

So I created my notification with php aritsan make: notification ContactConfirmation implements ShouldQueue:

    <?php

namespace App\Notifications;

use Illuminate\Bus\Queueable;
use Illuminate\Notifications\Notification;
use Illuminate\Contracts\Queue\ShouldQueue;
use Illuminate\Notifications\Messages\MailMessage;

class ContactConfirmation extends Notification implements ShouldQueue
{
    use Queueable;

    public $data;


    public function __construct($data)
    {
        $this->data = $data;
    }

    public function via($notifiable)
    {
        return ['mail'];
    }

    public function toMail($notifiable)
    {
        return (new MailMessage)
                    ->subject('Dúvida: '.ucfirst($this->data->subject))
                    ->greeting('Olá '.$this->data->name.'!')
                    ->line('Recebemos a sua mensagem e entraremos em contato assim que possível.')
                    ->line('Obrigado por usar a Mapa do Carro!');
    }

    public function toArray($notifiable)
    {
        return [
            //
        ];
    }
}

And the method that calls the notification in my Controller:

    public function sendEmail($data)
    {
        $user = \App\User::find(1);

        $data['name'] = $user->name;
        // Mail::to($guest->email)
  //                       ->queue(new ContactConfirmation($guest));

        $user->notify(new ContactConfirmation($data));


    }

When I submit the form a record is created in the jobs table with the notification information. But when I run the php artisan queue: work command it only keeps processing until it reaches the limit of attempts.

[2017-04-27 01:05:06] Processing: App\Notifications\ContactConfirmation
[2017-04-27 01:05:06] Processing: App\Notifications\ContactConfirmation
[2017-04-27 01:05:06] Processing: App\Notifications\ContactConfirmation
[2017-04-27 01:05:07] Processing: App\Notifications\ContactConfirmation
[2017-04-27 01:05:07] Processing: App\Notifications\ContactConfirmation
[2017-04-27 01:05:07] Processing: App\Notifications\ContactConfirmation
[2017-04-27 01:05:07] Processing: App\Notifications\ContactConfirmation
[2017-04-27 01:05:08] Processing: App\Notifications\ContactConfirmation
[2017-04-27 01:05:08] Processing: App\Notifications\ContactConfirmation
[2017-04-27 01:05:08] Processing: App\Notifications\ContactConfirmation
[2017-04-27 01:05:08] Processing: App\Notifications\ContactConfirmation
[2017-04-27 01:05:08] Processing: App\Notifications\ContactConfirmation
[2017-04-27 01:05:09] Processing: App\Notifications\ContactConfirmation
[2017-04-27 01:05:09] Processing: App\Notifications\ContactConfirmation
[2017-04-27 01:05:09] Processing: App\Notifications\ContactConfirmation
[2017-04-27 01:05:09] Processing: App\Notifications\ContactConfirmation

via Chebli Mohamed