This feature lets you restrict or allow user access to the Drupal site based on the domain of their email address. You can allow only users with specific domains if there are multiple users in your IdP. It secures your Drupal site by preventing users from other domains. You can either allow or block the domain.
Steps to enable/disable domain-based restriction:
Navigate to the Signin tab of the module
Check the option - Domain Restriction. the text box to enter the domain will appear.
Now select the radio button to allow/block domains as per your need.
Enter semicolon-separated domain names (E.g:- gmail.com, outlook.com, etc)
Scroll down and click on the Save Configuration button.