https://issues.redhat.com/browse/SAT-23437 changes the workflow for external users without a specified email.

Before, external users were always required to have an email associated with their account. With this change, the expected result is that external users will no longer be required to have an email associated with their account. Email will be required for both internal and external users only when "Mail Enabled" is enabled for the user account. (Note that email is never required for admin.)

Related Eng PR: https://github.com/theforeman/foreman/pull/10260