How are you managing the updaing of the email address on the user account(psoprdefn) for employees?

We are currently working towards rolling out Employee Self Service to our employees which will allow them to update their email addresses.    Currently we use their preferred as the email address on their login in account.    Obviously if the preferred is changed in ESS (Contact Details) that won't update their psoprdefn record which is good but how are others managing keeping the email address on psoprdefn updated.   As far as I can tell there is no way in PeopleSoft to do this and for security reasons (hacking) we wouldn't want to just assume an update to their preferred email was