5.7.1 <cluster_ovh>: Client host rejected: Access denied

Question

I'm currently working on an app with Zend Framework 3 hosted in OVH. I'm trying to send mail with Zend_Mail but without success... so here is my code :

$message = new Message();
$message->addTo('[email protected]')
        ->addFrom('[email protected]')
        ->setSubject('Test subject!')
        ->setBody("Test Body!");

// Setup SMTP transport using LOGIN authentication
$transport = new SmtpTransport();
$options   = new SmtpOptions();

$transport->setOptions($options);
$transport->send($message);

And In my SmtpOptions.php file :

protected $name = 'OVH';

/**
 * @var string
 */
protected $connectionClass = 'smtp';

/**
 * Connection configuration (passed to the underlying Protocol class)
 *
 * @var array
 */
protected $connectionConfig = [
   'ssl'      => 'ssl',
   'auth'     => 'login',
   'username' => 'my_username',
   'password' => 'my_pass'
];

/**
 * @var string Remote SMTP hostname or IP
 */
protected $host = 'ssl0.ovh.net';

/**
 * @var int
 */
protected $port = 465;

I've got an 5.7.1: access denied error and i can't figure out why ? Any help would be appreciate ! :) Let me know if it's not clear or if you need other informations.