there two big problems with editing the email address:
1) Duplicate email address
2) Invalid email address.
the Registration page already has validation in place to make sure a duplicate email address is not entered.
This is done by creating a recordset that is filtered on the email address that is entered, then using numeric validation to make sure that recordset is empty.
See the Registration page, especial the CheckRepeat recordset, and examine the server Validations server behavior for details on how it is configured.
you would want to duplicate this on the profile page.
Also, you would want to duplicate the email validation process and only update the email address once it is validated. examine the email that the registration page sends and the users_Confirm.php for details on how that works.