I tested this: in registration form - entered lower case email, then in login form entered email with first letter - a capital. The message was 'Invalid login'.
In registration form: ====================================================== auth.settings.table_user.email.requires=[ IS_LOWER(), IS_EMAIL(), IS_NOT_IN_DB(db,auth.settings.table_user.email) ] current.app.auth = auth form=current.app.auth.register() In login form ====================================================== auth.settings.table_user.email.requires=[ IS_LOWER(),IS_EMAIL(), IS_NOT_IN_DB(db,auth.settings.table_user.email) ] current.app.auth = auth form=current.app.auth.login(next=login_next) ======================================================