Can we remove users from the (prior) Classic environment now that they've been migrated to new OCI?

Summary:

Our users have been getting confusing emails asking them to change their password for the old (classic) environment PBCS.

Even if they do change their password, it will not work for the new OCI environment. What is the best way to stop these emails from the old environment?

Have you all had to remove your users from the old environment manually?

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