Hi,
I think that should be possible by extending the UIDBasedHomeFolderProvider class (or create a own implementaion of the HomeFolderProvider interface). In our class you could handle the email adress… After creating a new sping bean for this class you have to change a property in ldap-synchronisation.properties to point to your new beanID:
ldap.synchronisation.defaultHomeFolderProvider=yourHomeFolderBeanID
HTH
steffen