Microsoft KB Archive/932086

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Article ID: 932086

Article Last Modified on 8/15/2007


  • Microsoft Office Outlook 2007


Microsoft Office Outlook 2007 momentarily stops responding during typical operations. This includes when you read e-mail messages, move e-mail messages, or delete e-mail messages.

These symptoms are most noticeable during mail delivery or during synchronization. These symptoms become more pronounced as store size increases. They are more likely to occur when the size of the .pst file or the size of the .ost file approaches 2 gigabytes (GB). Additionally, they are more pronounced in a very large .pst file or in a very large .ost file that is 4 GB or larger.

Note When you perform the same operations in earlier versions of Outlook, the same performance problems do not occur if the .pst file or the .ost file is large.


To accommodate new features, Outlook 2007 introduced a new data structure for .pst files and for .ost files. In this new data structure, the frequency of writing data to the hard disk increases as the number of items in the .pst files or in the .ost files increases.

Note You cannot create a .pst file or an .ost file without this new data structure.


To resolve this problem, install the update that is described in the following article in the Microsoft Knowledge Base:

933493 Description of the update for Outlook 2007: April 13, 2007

Update 933493 is available to improve the general responsiveness of Outlook 2007 during common operations. These operations include reading, moving, deleting, and downloading e-mail messages for users who have large mailbox files (.pst files and .ost files) that are stored on their computers. From a technical perspective, this update optimizes the pattern in which Outlook 2007 writes to a large .pst file or to a large .ost file. This results in a reduction of disk access.

This update for Outlook 2007 is part of our continued commitment to improving our customers' product experiences. We are aware that some customers have encountered performance issues when they run Outlook 2007. This update incorporates several performance improvements. This update is designed to do the following:

  • Reduce the time that is required to copy or to move messages from one folder to another folder.
  • Increase the download speed when you download messages.
  • Reduce the time that is required to delete messages.


You can also use one of the following methods to resolve or minimize this problem.

Method 1: Reduce the size of the Exchange mailbox

If you reduce the size of the Exchange mailbox, the size of the .ost file will also be reduced. To reduce the size of the Exchange mailbox, do one or more of the following:

  • Delete items in your mailbox.
  • Archive items in your mailbox to one or more .pst files.

You can delete items or archive items manually. Alternatively, you can use Mailbox Cleanup. To use Mailbox Cleanup in Outlook 2007, click Mailbox Cleanup on the Tools menu. In the Mailbox Cleanup dialog box, you can use any one of the following features:

  • View mailbox size.
  • Find items that are older than a specified number of days.
  • Find items that are larger than a specified size.
  • Move old items to the archive file by clicking AutoArchive.
  • Empty the deleted items folder.
  • Delete all alternative versions of items in the mailbox.

Method 2: Use an online mode profile instead of a cached mode profile

Cached mode profiles use an .ost file to store the mailbox locally on the hard disk. If you have a large Exchange mailbox, you will have an .ost file that is even larger. For example, if the mailbox size is 350 megabytes (MB), the .ost file size can be 475 MB or larger.

Method 3: Split your large .pst file into several smaller .pst files

Outlook 2007 does not have a built-in function to split a .pst file into multiple .pst files. Therefore, you have to use one of the following steps to split a large .pst file:

  1. Use the Archive feature to move items to a new .pst file. To do this, follow these steps:
    1. In Outlook 2007, select your .pst file in the navigation pane.
    2. On the File menu, click Archive.
    3. In the Archive dialog box, click to select the Archive this folder and all subfolders check box, and then click a folder from the list.
    4. In the Archive items older than drop-down box, click a date.
    5. Click Browse, specify a path and a file name for the new .pst file, and then click OK.

      Note The new .pst file is displayed in the Mail Folders list as Archive Folders.

    If you want to change the display name for this .pst file, follow these steps:

    1. Right-click Archive Folders, and then click Properties.
    2. In the Archive Folders Properties dialog box, click Advanced.
    3. In the Personal Folders dialog box, enter the new display name in the Name box.
    4. Click OK two times to return to Outlook.
  2. Use the Move to Folder feature to move items to a new .pst file. To do this, follow these steps:
    1. On the File menu, point to New, and then click Outlook Data File.
    2. In the New Outlook Data File dialog box, click Office Outlook Personal Folders File (.pst), and then click OK.
    3. Specify a path and a file name for the new .pst file.
    4. In the Create Microsoft Personal Folders dialog box, specify the display name of the .pst file in the Name box. This is the name that is used by Outlook in the Mail Folders list.
    5. In the folder that contains the items that you want to move to a new .pst file, click one or more items to move.
    6. On the Edit menu, click Move to Folder.
    7. In the Move Items dialog box, click New.
    8. In the Create New Folder dialog box, enter a name for the new folder in the Name box.
    9. Under Select where to place the folder, click the new .pst file, and then click OK.
    10. In the Move Items dialog box, make sure that the new folder in the new .pst file is selected, and then click OK.

Method 4: Use a filter to restrict the items that you synchronize from Exchange to your .ost file

To configure a synchronization filter on a specific Exchange mailbox folder, follow these steps:

  1. Right-click the folder, and then click Properties.
  2. In the Properties dialog box, click the Synchronization tab.
  3. On the Synchronization tab, click Filter.
  4. In the Filter dialog box, specify the criteria that will be used to synchronize new items that you want to arrive in this folder.
  5. Click OK two times to return to Outlook.

Note This method will reduce the current size of the .ost file. Items that were previously synchronized in this folder will be removed from the local copy of your .ost file the next time that Outlook synchronizes this folder. These items will be removed if they do not fit the filter criteria. You may have to wait for background compaction to occur before you can see the size of your .ost file decrease. Alternatively, you can manually compact the .ost file by clicking the Compact Now button in the Advanced settings of the Exchange account.

If you use a synchronization filter, you can view the items that are not synchronized with the .ost file either by using Microsoft Office Outlook Web Access or by using an Outlook client that is configured to use online mode in an Outlook profile.

If you use a portable computer

If you are using a portable computer, you may experience these problems sooner than you would on a desktop computer. This occurs because hard disks on portable computers are generally slower than hard disks on desktop computers. The performance problems are directly related to hard disk speed. If you add more random access memory (RAM) to a computer, there is no effect on this problem.


For more information about Outlook .pst files, click the following article numbers to view the articles in the Microsoft Knowledge Base:

830336 The .pst file has a different format and folder size limit in Outlook 2007 and in Outlook 2003

832925 How to configure the size limit for both (.pst) and (.ost) files in Outlook 2003

Note The registry path that is used in article 832925 is for Outlook 2003. For Outlook 2007, use the \12.0 path instead of the \11.0 path that is mentioned in the article.

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