ZF3 Inject part of global config into a service factory

I have a service defined in Module.php, where I inject my mail config, defined in config/autoload/global.php this way:

public function getConfig()
{
    return include __DIR__ . '/../config/module.config.php';
}

public function getServiceConfig()
{
    return [
        'factories' => [
            'Mailer' => function($container) {
                return new MailService($this->getConfig()['mail']);
            },

        ]
    ];
}

But I want to do it the ZF3 way (which I'm learning, so I defined my service in my module.config.php this way:

return [
    'services' => [
        'factories' => [
            Service\MailService::class => MailServiceFactory::class
        ]
    ],

And my MailServiceFactory.php is:

class MailServiceFactory implements FactoryInterface
{
    public function __invoke(ContainerInterface $container, $requestedName, array $options = null)
    {
        return new MailService();
    }
}

But how can I retrieve my config defined in global.php and inject it in the factory, needed by my service?

OK, after some debug and var_dump(), I have it. I can access the config array thanks to $container->get('configuration'). So my factory is now:

class MailServiceFactory implements FactoryInterface
{
    public function __invoke(ContainerInterface $container, $requestedName, array $options = null)
    {
        $config = $container->get('configuration');
        return new MailService($config['mail']);
    }
}