Internal user domains help the policy distinguish your organization's employees from external users.
For example, if your organization's email domain is @company.com, you can configure it as an Internal User Domain. This helps ensure that users from your organization's own domain are treated as internal rather than being incorrectly identified as external.
This is especially useful when external email domains are also configured. Defining your internal domains provides an additional way to keep the findings accurate and focused on users who are actually external to your organization.