Change User / Case Manager's Email Address
This article goes over how-to change case manager's email by case manager themselves or by an admin user.
Go to 'Setup' and then 'Settings' from the main left menu. Under 'Setup' select 'Case Managers':
Select the case manager that you want to change their email (if you're an admin). Click on 'Edit' under their 'Case Manager Info'. Change the email address and click 'Save':
A case manager can do the same for their own email address by going to 'My Settings' >> 'Case Manager Info' >> 'Edit'.