By default, Instant Messaging server performs an anonymous search of the LDAP directory. However, it is common for sites to prevent anonymous searches in their directory so that any random person cannot do a search and retrieve all the information. If your site’s directory is configured to prevent such anonymous searches, and you didn't provide bind credentials during post-installation configuration, you need to configure the Instant Messaging server needs with a user ID and password it can use to bind and perform searches.
Use the iim_ldap.usergroupbinddn and iim_ldap.usergroupbindcred parameters to configure the necessary credentials.
See iim.conf File Syntax for instructions on locating and modifying iim.conf.
Specify the DN you want the server to use to bind to the directory as the value for iim_ldap.usergroupbinddn.
Specify the password that corresponds to the bind DN as the value for iim_ldap.usergroupbindcred
Save and close the file.