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Article ID: 179870 - Last Review: January 12, 2015 - Revision: 2.0

This article has been archived. It is offered "as is" and will no longer be updated.

NOTE: These procedures only apply if you have installed Outlook with the Internet Mail Only option. To determine your installation type, click About Microsoft Outlook on the Help menu. If you have the Internet Mail Only option installed, you see "Internet Mail Only".

For information about the differences between Microsoft Outlook and Microsoft Outlook Express e-mail clients, click the following article number to view the article in the Microsoft Knowledge Base:
257824  ( ) OL2000: Differences Between Outlook and Outlook Express

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This article describes how to compact the Personal Folders file(s) (PST) in Microsoft Outlook, to eliminate deleted item space and recover room on your hard disk.

More information

To conserve space on your computer's hard disk, you can delete unwanted items from the various PST folders and then compact the files to make them smaller.

NOTE: Deleting the unwanted items from each folder only moves them to the Deleted Items folder, which is in the same file. You must delete the items from the Deleted Items folder to permanently delete them, so that Outlook can compact the file.

The compacting process does not remove all the free space from the file. It leaves either 16 kilobytes (KB) or 4 percent of the file size (before compacting) whichever is greater.

To be compacted, a file must meet the following requirements:

  • The file must be 16 KB or larger.

  • The file must have at least 16 KB of space freed since the last time it was compacted.
You can start Outlook file compaction manually, or run it automatically in the background.

Automatic Background Compaction

PST files that are not on your computer may require manual compaction, due to interactions between the computer where the PST files are stored and your computer.

Automatic compaction takes place as an idle task in the background. The following conditions must be true for this background task to take place:

  • Outlook must be running. -and-

  • The computer must not be engaged in other CPU-intensive tasks such as copying or downloading files.

To Manually Start PST Compaction

  1. If the Folder List is not showing, click Folder List on the View menu.
  2. Right-click one of the Personal Folders.
  3. Click "Properties For Personal Folders."
  4. On the General tab, click Advanced, and then click Compact Now.
  5. Click OK twice.

Applies to
  • Microsoft Outlook 98 Standard Edition
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