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How to compact an Outlook data file (*.pst)

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› Tutorials › How to compact an Outlook data file (*.pst)

Last reviewed on March 12, 2020     2 Comments

Applies to: Outlook 2019 (Win), Outlook 2016 (Win), Outlook 2013, Outlook 2010

Outlook will compact the pst automatically when the amount of "white space" (space used by deleted items) exceeds 20% and it has some idle time. Outlook will work on compacting the pst when it and other programs aren't using all of your computer's resources and in most cases, it will recover the space within minutes, often starting as soon as you emptied the Deleted Items folder. However, if you deleted a large message (many MB in size), it could take hours or days to recover all of the file space no longer used by the message.

If you want to reclaim the space immediately, you can run Compact manually. Under normal circumstances, it will take several seconds to several minutes to complete the compact process but if a single message was huge (multiple MB), Outlook may seem to stop responding when it is compacting the space used by that message.

To compact manually in any version of Outlook:

  1. Right-click on the root folder of the pst file and choose Properties.
    Properties - Advanced dialog
  2. Click the Advanced button to open the Outlook Data File dialog.
  3. Click the Compact Now button.
    Compact Now in Outlook

How to compact an Outlook data file (*.pst) was last modified: March 12th, 2020 by Diane Poremsky
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Related Posts:

  • How to Compact the Data File When you Close Outlook
  • Recover messages deleted from .pst files
  • How to Export Outlook Data to a PST File
  • Recover Deleted Items in OWA

About Diane Poremsky

A Microsoft Outlook Most Valuable Professional (MVP) since 1999, Diane is the author of several books, including Outlook 2013 Absolute Beginners Book. She also created video training CDs and online training classes for Microsoft Outlook. You can find her helping people online in Outlook Forums as well as in the Microsoft Answers and TechNet forums.

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Patricia Dowden (@guest_213087)
April 13, 2019 10:33 am
#213087

Diane: "The operation cannot be performed because the message has been changed" Outlook 2016
How to stop this problem with draft messages? I found one post that blames it on Kaspersky AddIn, but this is disabled on my system.

Thanks, Pat

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Diane Poremsky(@diane-poremsky)
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Reply to  Patricia Dowden
April 13, 2019 11:24 pm
#213091

I don't think any addin is doing it - its outlook. It sends the changes back to the server but is not getting the response back or doesn't register it until you select another message then come back to the original one. That is the only solution I am aware of at this time.

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