Applies to: Exchange Server 2007 SP1, Exchange Server 2007
Topic Last Modified: 2007-10-26

This topic will help you diagnose and resolve issues where Microsoft Office Outlook and Microsoft Entourage for Mac users experience poor performance when they work with a folder that contains many items on a server that is running Microsoft Exchange Server 2007, Exchange Server 2003, or Exchange 2000 Server. When this issue occurs, Outlook and Entourage users may receive one of the following messages:

This issue occurs when an Outlook or Entourage user works with items in a folder that contains many items. Outlook must perform several operations on the Exchange server to retrieve the contents of a folder. Entourage must retrieve or synchronize content from the Exchange server. Therefore, when there are many items in a folder, additional processing is required to respond to the Outlook requests. This issue may also occur when Outlook or Entourage users view another Exchange user's calendar or contacts folder.

You can help avoid poor performance in Outlook or Entourage by carefully managing the number of items in a single folder, especially the folders that are heavily used. These folders include the Inbox, Calendar, Tasks, and Sent Items folders and any other folders that may be heavily used by Outlook or Entourage users in your Exchange environment. Item management is particularly critical for calendars that are accessed by many users and delegates, or in environments where meeting requests are heavily used.

The recommended number of items in a folder depends on several factors. These factors include the client's proximity to the server, the storage infrastructure, the load on the hard disks, the number of users, and the number of restricted views.

We recommend that you maintain a range of 3,000 to 5,000 items in a folder depending on the capacity of the Exchange environment. Additionally, you can create more top-level folders or create subfolders underneath the Inbox and Sent Items folders. When you do this, the costs that are associated with index creation will be greatly reduced if the number of items in any one folder does not exceed 5,000. The following list includes ways that you can help manage the number of items in folders:

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