(Required) Instant Messaging uses an LDAP server, such as Directory Server, for end user authentication and search. In a deployment with Portal Server, Instant Messaging uses the same LDAP server used by Portal Server. If you do not have an LDAP directory already installed, you must install one.
The Instant Messaging server does not store the Instant Messenger end-user authentication information. This information is stored in the LDAP server.
By default, the Instant Messaging server relies on the common end-user attributes cn and uid to search for end-user and group information. If you want, you can configure the server to use another attribute for search. In addition, Instant Messaging properties (such as contact lists and subscriptions) can be stored in files on the Instant Messaging server or in the LDAP server.
For instructions on configuring the server to use a non-default attribute for user search, see the Sun Java System Instant Messaging 7.2 Administration Guide.
Because a proper Directory Server implementation is instrumental to a successful Instant Messaging deployment, also see the Directory Server documentation: