How can we get all of the indexes values inside the $config variable from a specific custom config file?

Question

I have created a config file named email.php inside application/config folder. Now I want to assign my variable $email_config to all the indexes of the $config variable inside my email.php config file.

I have tried to use $email_config = $this->config->config; but this will get all the indexes values of $config variable from every config files under the config folder..I don't want that, I only want the indexes values inside my email.php file