You experience slow performance when you create many contacts by using Exchange Web Services (EWS) in a Microsoft Exchange Server 2010 environment. When this issue occurs, the global catalog server replies slowly to Lightweight Directory Access Protocol (LDAP) requests.
Note This issue always occurs when you migrate mailboxes to an Exchange Server 2010 server.
This issue occurs because EWS issues two LDAP requests for each contact. EWS issues one request for the mailbox in which you create the contact and one request for the contact that you create. Therefore, the global catalog server experiences a heavy workload when you create many contacts at a same time, and the global catalog server replies slowly to LDAP requests.
To resolve this issue, install the following update rollup:
2661854 Description of Update Rollup 2 for Exchange Server 2010 Service Pack 2
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.