Unfortunately, you cannot change your email address, only your password. You can, however, designate another email as a secondary email for notifications and password changes. From the main evony...
Go under 'my gaia' 'account settings' 'preferences'
You delete the old e-mail in the e-mail box.
You also have to change your password though.
It's required.
If you want to delete an email address from your outlook auto fill you start by typying the email address then scroll down with your arrow key to highlight the address then press the delete key.