Active Directory

Select this option to use the Active Directory directory service as the Lightweight Directory Access Protocol (LDAP) server. To manage mailboxes, use Active Directory Users and Computers.

Site Server Membership Directory

Use this option when you have installed Microsoft LDAP Service as part of Microsoft Commercial Internet System 2.0 Mail and you are using it to manage mailboxes.

Exchange LDAP Service

Select this option to use a Microsoft Site Server 3.0 LDAP server to manage mailboxes.