Unique overlay confusing

Hi there, I've followed the docs (and some forums), and made these modifications: (OpenLDAP doc: http://www.openldap.org/doc/admin24/overlays.html#Attribute%20Uniqueness) dn: cn=module,cn=config cn: module objectClass: olcModuleList olcModulePath: /usr/lib/ldap/ olcModuleLoad: unique.la dn: olcOverlay=unique,olcDatabase={1}mdb,cn=config objectClass: olcOverlayConfig objectClass: olcUniqueConfig olcOverlay: unique olcUniqueAttribute: uid olcUniqueAttribute: mail olcUniqueAttribute: uidNumber olcUniqueAttribute: sn olcUniqueAttribute: cn but I still can set the mail attribute as same e-mail address for two different users. I've tried this config too: dn: olcOverlay=unique,olcDatabase={1}mdb,cn=config objectClass: olcOverlayConfig objectClass: olcUniqueConfig olcOverlay: unique olcUniqueUri: ldap:///?uid?sub? olcUniqueUri: ldap:///?mail?sub? olcUniqueUri: ldap:///?uidNumber?sub? olcUniqueUri: ldap:///?sn?sub? olcUniqueUri: ldap:///?cn?sub? What em'I missing? Thanks, a.