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How to compact PST and OST files to eliminate deleted item space in Outlook
Article ID: 289987 - View products that this article applies to.
This article was previously published under Q289987
For a Microsoft Outlook 2000 (IMO) version of this article, see 196890
For a Microsoft Outlook 98 (CW) version of this article, see 179868
For a Microsoft Outlook 98 (IMO) version of this article, see 179870
This article describes how to compact personal folders (.pst) files or offline store (.ost) files in Microsoft Outlook to eliminate deleted item space and recover room on your hard disk.
To conserve space on your hard disk, you can delete unwanted items from the various .pst and .ost files, and then compact the files to make them smaller.
Note When you delete the unwanted items from each folder, it 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 .pst or .ost file must meet the following requirements:
Automatic Background CompactionAutomatic compaction takes place as an idle task in the background. The following conditions must be true for this background task to take place:
How to Manually Start PST Compaction
Microsoft Office Outlook 2010
How to Manually Start OST CompactionUse one of the following methods:
Method 1: Microsoft Office Outlook 2007
Method 2: Microsoft Office Outlook 2003 and earlier versions of Outlook
Method 3: Microsoft Office Outlook 20101. Delete any items that you do not want to keep, and then empty the Deleted Items folder.
2. Click on File Tab in the Ribbon and Select Info tab in the Menu
3. Click on Accounts Settings tab, Click on Account Settings again
4. In the list, select Microsoft Exchange Server, and then click Change.
5. Click More Settings.
6. On the Advanced tab, click Offline Folder File Settings.
7. Click Compact Now.