Mailgun and laravel 5.2

I try to use mailgun and laravel 5.2 without success.

I created an account in mailgun.com. I validated the email adress and the phone number.

Here an axtract of what I see in mailgun.com :

In .env file, I entered that :

In services.php file, I have :

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

And at least in mail.php file, I have :

  'driver' => env('MAIL_DRIVER', 'smtp'),

And to send my email i code :

Mail::send('emails/emailValidationInscription', [
            'personne' => $personne
        ]
        , function($message) use ($personne)
        {
            $message->to($personne->email);
            $message->subject('validation inscription');
        });

It does not work, I have this error :

cURL error 60: SSL certificate problem: unable to get local issuer certificate

What's the problem ?

Thanks for your answers.

Dominique

via user2672338