The LDAP Advanced tab lets you configure rarely used settings for the LDAP server component..
If the By default return all available attributes option is checked, then if an LDAP client doesn't specify which attributes it wishes, VPOP3 will give it all the available attributes. If this option is not checked, VPOP3 will only return a restricted set of attributes. This option should always be turned on.
With VPOP3 Enterprise, you can tell VPOP3 to access an external address book database using an ODBC driver, VPOP3 can then provide contact details from this external database to people using the VPOP3 LDAP or Webmail services. This is an advanced feature and requires you to install and configure a suitable ODBC driver on the VPOP3 computer and know details of the database schema you are connecting to. See the ODBC Database topic for more information.