According to the User Guide1, the steps to configure End-User Access to the Spam Quarantine via LDAP are as follows:

On the ESA, choose System Administration > LDAP > LDAP Server Profile page.

Click Add LDAP Server Profile.

Enter a name for the profile and click Submit.

Click Add Query.

Enter a name for the query and click Submit.

Configure the query settings, such as server address, port number, base DN, scope, filter, and attributes.

Check the Spam Quarantine End-User Authentication Query check box. This is the suboption that enables LDAP authentication for end users who access the spam quarantine.

Check the Designate as the active query check box. This is the suboption that specifies which query to use for end-user authentication. Only one query can be active at a time.

Click Submit and commit changes.

On the ESA, choose Monitor > Spam Quarantine > End-User Quarantine Access.

Check the Enable End-User Quarantine Access check box.

Choose LDAP from the End-User Authentication drop-down list.

Select the LDAP profile and query that you created earlier from the drop-down lists.

Click Submit and commit changes.