KB Article – Repair Outlook Data Files (PST & OST)

Repair Outlook Data Files (PST & OST)

Document ID: KB-OUT-DATA-001
Version: 1.0
Date: 27/08/2025
Author: Ante Crvelin
Audience: IT Infrastructure, Service Desk, End Users
Scope: Applies to Microsoft Outlook 2007, 2010, 2013, 2016, 2019, and Office 365 (Makita AU).

1. Overview & Purpose

Outlook data files (.pst and .ost) may become corrupted, preventing Outlook from opening mailboxes or folders. This KB outlines how to use the built-in Inbox Repair Tool (SCANPST.EXE) to diagnose and repair data file errors.

Common scenarios where repair may be needed:

Outlook displays: “Cannot open your data file.”
Outlook displays: “Cannot open the set of folders.”
Suspected data file corruption.

For Exchange accounts, the .ost file can simply be deleted, and Outlook will recreate it automatically upon restart.

2. Prerequisites

Ensure Outlook is closed before running repairs.
Backup the .pst/.ost file before attempting repairs.
Administrative access may be required.

3. Procedure

Step 1 – Locate Outlook Data Files

Default path for .pst/.ost files:

C:\Users\%username%\AppData\Local\Microsoft\Outlook

Step 2 – Locate SCANPST.EXE

The location of scanpst.exe depends on your version of Outlook:

Office 365 / Outlook 2019 / Outlook 2016 (Click-to-Run):
C:\Program Files\Microsoft Office\root\Office16\
Outlook 2016 (MSI Volume License):
- 32-bit Windows → C:\Program Files\Microsoft Office\Office16\
- 64-bit Windows → C:\Program Files (x86)\Microsoft Office\Office16\
- 64-bit Outlook → C:\Program Files\Microsoft Office\Office16\
Older Versions:
- Outlook 2013 → C:\Program Files (x86)\Microsoft Office\Office15\
- Outlook 2010 → C:\Program Files (x86)\Microsoft Office\Office14\
- Outlook 2007 → C:\Program Files (x86)\Microsoft Office\Office12\

Step 3 – Run the Inbox Repair Tool

Exit Outlook.
Open SCANPST.EXE from the version-specific folder.
Select Browse to locate the data file (.pst).
Click Start to begin scanning.
If errors are found, select Repair.
- By default, a backup (.bak) file is created.
- To rename or relocate, enter details in Enter name of backup file.

👉 Multiple repair attempts may be required for severely corrupted files.

Step 4 – Post-Repair Behaviour

If the repair is successful, Outlook should open normally.
A folder named "Recovered Personal Folders" or "Lost and Found" may appear, containing items that were not restored to their original folders.

Step 5 – Recovery Options

Create a new Outlook Data File
- Move items from Lost and Found to a new .pst file.
- Remove the old corrupted file after migration.
Recover from the .bak file
1. Navigate to the .bak file created during repair (e.g. user@domain.com.bak).
2. Rename it to .pst (e.g. user@domain.com.bak.pst).
3. Import into Outlook using File > Open > Import/Export > Import from another program/file.

4. Validation / Testing

Launch Outlook and confirm it opens without errors.
Verify access to all expected folders and mail items.
Check if any folders were moved into Recovered Personal Folders.

5. Troubleshooting

If repeated repairs fail, create a new Outlook profile and import recovered data.
Large files may take a significant amount of time to scan and repair.
Data permanently corrupted may not be recoverable.

💡 Makita Service Desk Tip

For Exchange/Office 365 mailboxes, it is often faster to delete and re-download the .ost file instead of repairing it. Outlook will recreate the file on next launch.
Always backup .pst files before running SCANPST.EXE – repairs can occasionally truncate files.
If users report very large data files (>10GB), recommend archiving or splitting mailboxes before repair to reduce corruption risk.
When troubleshooting remotely, ask the user to confirm whether they’re on 32-bit or 64-bit Office to ensure the correct SCANPST.exe path is used.

6. Risks / Considerations

Repair may result in partial recovery only.
Items in Lost and Found may need manual reorganisation.
Running repairs multiple times can stress large files (>10GB).