This issue occurs if you have the Check Point Next Generation firewall program installed in your Active Directory directory services forest.
When you use Active Directory Users and Computers to create a new user together with an Exchange mailbox, Active Directory is queried to enumerate the object classes in the schema. One of the queries that Exchange performs has the following Lightweight Directory Access Protocol (LDAP) filter:
(|(adminDisplayName=user)(lDAPDisplayName=user))
When Next Generation firewall is installed, it adds a new schema class of
fw1person together with a new object class to the schema. This object class has an
adminDisplayName property set to
user. Therefore, when Exchange 2000 queries Active Directory during the mailbox creation process, two objects are returned instead of one object as Exchange 2000 expects. Because of this behavior, the mailbox is not created successfully. If you run a similar query by using the
Ldp.exe command, two objects that are similar to the following objects are returned:
CN=fw1person,CN=Schema,CN=Configuration,DC=example,DC=com
CN=User,CN=Configuration,DC=example,DC=com