This setting is useful in the following two cases:
- WordPress Extranet
- WordPress Network (= Multisite) installation
As it will restrict access to users from whitelisted domains.
The plugin will compare the SMTP email domain of each user when signing in (and when creating a user the first time he or she signs in) with the white listed domains and only grant access when users come from a domain entered in the list.
You can add one domain in the form example.com per line. Don’t confuse the domain’s URL e.g. https://www.example.com with its so-called top-level domain example.com.
Important After you entered a new entry in the input box you must click “+” to add it. Also when you are entering just one line.