In a Microsoft Exchange Server 2007 environment, a user tries to copy or move items from one public folder to another public folder by using Microsoft Office Outlook. In this situation, the operation takes a long time. For example, it may take one minute to copy 500 items from one public folder to another public folder in an Exchange Server 2003 environment. However, it may take ten minutes in an Exchange Server 2007 environment.
This problem occurs because of a change in the Information Store security model in Exchange Server 2007. An additional operation that is not present in Exchange Server 2003 occurs each time notifications are sent to Outlook clients. If there are lots of Outlook clients that are viewing the source public folder or the destination public folder when the copy operation is performed, the copy operation performs inefficiently. This is because a notification is sent to every client for every item that is copied. This new operation is performed for each notification. Additionally, Active Directory is contacted each time when it is executed instead of caching the result
To resolve this problem, install the following update rollup:
2279665 Description of Update Rollup 1 for Exchange Server 2007 Service Pack 3
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.