We have excahnge 200 enterprise server running on windows 200 server.We have 500 users already running.We tried adding more users but we received an error "Windows cannot create e object because;The directory service has exhausted the pool of relative identifiers" Can anyone explain ?

Check which domain controller holds the RID-Master... It looks like you may have to seize that role onto another DC. M$: "Relative Identifier Master You can create a new security principal object (User, Group, or Computer) on any domain controller. However, after creating several hundred security principal objects, a domain controller must communicate by means of RPC with the domain controller holding the domain's RID master role before creating the next security principal object. Then, another several hundred security principal objects can be created, and when this set of objects has been created, the process of contacting the RID master repeats. If a domain controller's RID pool is empty, and the RID master is unavailable, you cannot create new security principal objects on that domain controller. When using Active Directory Users and Computers snap-in to create new objects, a message similar to the following displays when the domain controller's RID pool is empty and the domain's RID master is unavailable: Active Directory Service The object James Smith could not be created. The problem encountered was: The directory service has exhausted the pool of relative identifiers. "