cURL error 60: SSL cert with Laravel + Mailgun

I am using Mailgun + Mail class in laravel 5.2 in this sample code:

Mail::send('emails.send', ['title' => $title, 'content' => $content], function ($message)
                {

                    $message->from('hello@mywebsite.com', 'Marcos');

                    $message->to('amldesign@gmail.com');

                });

I´m catch the $e Exceptions and laravel return me this error:

cURL error 60: SSL certificate problem: unable to get local issuer certificate (see http://ift.tt/1mgwZgQ)

I think that the services.php config is right:

'mailgun' => [
        'domain' => env('MAILGUN_DOMAIN','mywebsite.com'),
        'secret' => env('MAILGUN_SECRET'),
    ],

What is the problem?

via Chebli Mohamed