My wife recently upgraded to Windows 10. Not super fast, and think it is time for a fresh install. Looking for files to save and came across a 5+ GB PST file. Had her delete about 80% of them, and the C:\Users\mywife\AppData\Local\Microsoft\Outlook\Outlook.pst file is still the same size. How do I reduce the size of this file?

EDIT. I have since taken steps outlined by Morten. As seen by the below, it should be only around 0.3 GB, not 5 GB.

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The file will eventually automatically get reduced in sized ("compact'ed") by Outlook if you leave the PC idle with Outlook open, and the PST loaded.

You can also do it manually though. I've slightly edited the following guide from MS. You can checkout the whole guide here

Manually reduce the size of an Outlook Data File (.pst)

If you delete items from an Outlook Data File (.pst), the file is automatically compacted in the background when you’re not using your computer and Outlook is running. You can also manually start the compact command immediately.

  1. Delete any items that you do not want to keep.

  2. Open the Folder List view. At the bottom of the Navigation Pane, click the Folder List icon or press CTRL+6.

  3. In the Navigation Pane, right-click the Deleted Items folder, and then click Empty Folder.

  4. Click the File tab.

  5. Click Account Settings, and then click Account Settings.

  6. On the Data Files tab, click the data file that you want to compact, and then click Settings.

  7. Click Compact Now.


While the above should work in most cases, it didn't in this particular case. It might be that the PST file has some kind of damage. Microsoft suggests trying to fix this by running the Inbox repair tool "scanpst.exe".

This utility can be found in different places depending on your Windows version (32 or 64 bit) and also the Office version:

Outlook 2013

  • 32-bit Windows C:\Program Files\Microsoft Office\Office15
  • 64-bit Windows C:\Program Files (x86)\Microsoft Office\Office15
  • 64-bit Outlook C:\Program Files\Microsoft Office\Office15

Outlook 2010

  • 32-bit Windows C:\Program Files\Microsoft Office\Office14
  • 64-bit Windows C:\Program Files (x86)\Microsoft Office\Office14
  • 64-bit Outlook C:\Program Files\Microsoft Office\Office14

Outlook 2007

  • 32-bit Windows C:\Program Files\Microsoft Office\Office12
  • 64-bit Windows C:\Program Files (x86)\Microsoft Office\Office12

In the folder matching your Windows / Office version, will be the "scanpst.exe" file. Simply double-click, browse to the PST file and click "Start" (be sure to close Outlook before doing this).

Scanpst interface

After the tool is finished running, close it down, open Outlook again and repeat the compress procedure outlined above.

  • Thanks Morten, Completed all steps, but still 5GB. – user1032531 Aug 7 '15 at 14:39
  • That's very odd. I'm afraid I don't have any more tips - only thing I can think of is perhaps your mailbox really is at 5 GB. It will be mainly the emails with attachments that take up space, so perhaps the emails that were removed where the ones without attachments. It's a long shot though, sorry I can't help any further. – Morten Kirsbo Aug 7 '15 at 14:59
  • Thanks Morten, Yes, odd! Files with big attachments were removed first, so that isn't it. I did update my original post to show the actual size. – user1032531 Aug 7 '15 at 15:02
  • I think your PST file might be corrupt. I have updated my answer with instructions on how to scan and fix the file using Microsoft's inbox repair tool (scanpst.exe). After running the app, you need to repeat the compress procedure. Not sure it will work, but it's certainly worth a shot. – Morten Kirsbo Aug 7 '15 at 16:57
  • One thing to note: Do take a backup of the PST file before running scanpst.exe. The app shouldn't break anything, but you never know! – Morten Kirsbo Aug 7 '15 at 17:03

protected by Community Sep 15 '18 at 6:18

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