For security reasons, it's not possible for account administrators to change the email address of registered (invitation accepted) users. Only users themselves may change their address. Then a project owner can invite them under their new address.
This is the recommended procedure:
- A project owner sends a new invitation to the user's new email address as described in Adding people to projects.
- The user logs in with their old email address and changes it to their new email address as described in Adjusting your profile settings.
- The user accepts the new invitation. The user will receive notifications only at the new email address.