Hi,
Thank you for reaching out to us.
You can only allow the users with a custom domain to access your site by using our Domain Restriction feature. This Domain Restriction feature is available in the paid ( both standard and premium ) version of the plugin and not in the free plugin.
If you want to check out the premium features then we can set up a demo. Please let us know about your availability accordingly we can set up a demo.
If you have any further questions please reach out to us at info@xecurify.com
Thanks