Email is not secure but sending an email with a link to "Information about your appointment" is fine. If that link goes to `/appointments/sjdhfaskfhjaksdjf`, there is no leaked data. If it goes to `/appointments/20251017lkafjdslfjalsdkjfa`, then the link itself contains PHI.

Whether creation date is PHI…I could see the argument being yes, since it correlates to medical information (when someone sought treatment, which could be when symptoms present.)