Hiding website from the world except for users with a certain email address?

I am looking for a solution where a Webflow site can be hidden from the world except for users with a particular email address login, working with a client who has requested this functionality in order to restrict access to their website content except for their staff.

Been looking a few external integration products magic.link & memberstack but having looked at the documentation don’t specifically offer a way of allowing users with specific email address to access. Does anyone know of any services/integrations like this?

Would be great to hear if someone has worked on any similar intranet/internal websites with Webflow and how they tackled this problem for their clients. Thanks in advance.