One of the SIMS major components is the Sun Directory Service (also referred to as the SunDS, the LDAP directory service, or simply the directory service). SunDS is an implementation of a directory service based on the Lightweight Directory Access Protocol (LDAP). SunDS maintains a directory of user and distribution list information, as well as configuration data for Sun Messaging Connectivity Services channels (SMCS). The SunDS provides address information used by the IMTA to deliver messages.