In order to change or correct the Primary email address for an End-User (Zendesk User), you must be able to create a secondary email address.
You cannot create a secondary email address for the user until the Primary email address has been Verified. Use the following procedure to update or correct the primary email address for the user:
1. In the drop-down next to the user email address, click the "Verify now" option.
2. Create a secondary email address (the address you want to make the primary address for the user) via the "+add contact" option.
You should now have two email addresses for the user.
3. Make the new email address the Primary via the drop down menu next to the address.
4. Delete the old Primary email address via the drop down menu.