I created the next class:
//src/AppBundle/Services/RegisterMail.php
namespace AppBundle\Services;
class RegisterMail{
    protected $mailer;
    public function __construct($mailer)
    {
        $this->mailer = $mailer;
    }
    public function sendPassword(){
         $message = \Swift_Message::newInstance()
            ->setSubject('Otro correo')
            ->setFrom('fromEmail@fromEmail.com')
            ->setTo('toEmail@toEmail.com')
            ->setBody('hola desde el servicio')
        ;
        $envia = $this->mailer->send($message);
    }
}
And I declare it as a service in my services.yml
services:
    registermail:
        class: AppBundle\Services\RegisterMail
        arguments: [@mailer]
In my controller call the service:
//src/AppBundle/Controller/DefaultController
namespace AppBundle\Controller;
use Symfony\Bundle\FrameworkBundle\Controller\Controller;
use Sensio\Bundle\FrameworkExtraBundle\Configuration\Route;
class DefaultController extends Controller
{
    /**
    * @Route("/")
    */
    public function indexAction()
    {
        //Envío el email con el password
        $mailer = $this->get('registermail');
        $mailer->sendPassword();
        return $this->render(':Default:index.html.twig');
    }
}
The email are sent, but the page still loading 30 seconds, and I have an alert from developer toolbar: "An error occurred while loading the web debug toolbar (404: not found). Do you want to open the profiler? If Accept the message symfony profiler don't show any error. If Cancel the message developer toolbar don't appears.
What am I doing wrong?
Thank you!
 
     
    