You can change your email address from within the game by heading to the profile/account section and tapping the edit button beside your email and entering your current password for verification. 

If you have trouble with this, [lease contact us through the in game "Contact Support" feature providing your old & new email addresses, and one of our support staff will be happy to help.

If you're unable to log into your account, please submit a support request and we'll get back to you shortly.