There are two emails potentially associated with a brainCloud user account:
- email identity - which is used to log in - which is edited via this call - http://getbraincloud.com/apidocs/apiref/index.html#capi-identity-changeemailidentity
- contact email - which is an email associated with a user for the purpose of sending emails to them - it is updated using this call - http://getbraincloud.com/apidocs/apiref/index.html#capi-playerstate-updatecontactemail
Note that when you first attach an email identity to a user, the system will also set that's contact email to the same email address (if it's blank). It doesn't overwrite the email if it already had a value.
This means, that if you are updating a users's email identity, you will probably also want to update their contact email directly as well (so use both calls in that case).