If you have unlimited user license, external table/SA System implementation may be the best option. in order to distribute the content through agent/email.
If the user is maintained in Active Directory / Weblogic LDAP it will become easy to add the role/group in recipients. If presentation catalog group is defined then you may require user to login once to include the user in the presentation group.
Alternatively, if you have just handful of users, 11g gives an option to include email addresses in the agent distribution list. If you have data level security then you must have the user exist in presentation catalog / LDAP store.
hope this helps..