View federated-authentication user name conflicts in Apple School Manager
After a domain is successfully added, Apple School Manager reviews all existing Apple IDs by searching for any using that specific domain name. If an Apple ID is found to be using the domain name, Apple School Manager lets you send an email to that person, and a notification to any device connected to their iCloud account, letting them know they must update their Apple ID username so that you can use it for your institution. They do not have to change their password and all their purchases and data remain in their account.
For example, say your institution registered the domain townshipschools.org.uk several years ago and set up email addresses for all their employees. Jane Appleseed decided to use the email address she was assigned 'email@example.com' as her personal Apple ID.
Even if Jane no longer works for the institution that registered townshipschools.org.uk, she still has the Apple ID with that domain name. Because you are setting up federated authentication for the domain name townshipschools.org, Jane must change her Apple ID username so you can create the Managed Apple ID firstname.lastname@example.org if you want.
View federated authentication username conflicts
In Apple School Manager , sign in with an account that has the role of Administrator, Site Manager or People Manager, then tap Activity.
Tap Checking for Conflicts.
If any username conflicts are found, you will see a dialogue with the total number of username conflicts.
Tap Continue, tap Send Notifications, then tap OK.
A mail message is sent to each user with a username conflict, as well as a notification to any device connected to their iCloud account, letting them know they must change their personal Apple ID.
You can view the process of sending mail messages to users with a username conflict in the Activity section of Apple School Manager.