Whitelist makes making password-protected / members only wordpress sites a breeze. It creates a Roadblock on your site allowing only whitelisted users to get through. It’s also perfect for wordpress websites that are in alpha / beta /testing phase where owners can invite only a specific set of users by email to test out the website. Apart from the Roadblock spam visitors can be blocked by enabling the Recaptcha that this plugin provides.
Once you activate the plugin your website will be blocked to everyone and visitors would be shown a Roadblock page where they can enter their email to visit your site. If their email is on the whitelist they’ll be given the option to create a password and login to your site.
Check it out on the WordPress repo: https://wordpress.org/plugins/fifthsegment-whitelist/
The Roadblock page