This plugin can help you gate some pages such as the Subscription Portal page to logged in WordPress users only. If someone is not logged in, you can redirect them to the login page.
This plugin can help you create a custom Login page
This plugin can help you customize emails that will be sent to your WordPress users
The restrict user access plugin does not work on WordPress sites that are hosted on wordpress.com
Details on: http://wpcomstaging.com
Wordpress.com support: https://en.support.wordpress.com/domains/