How to Repair a Corrupted Outlook Data File Without Losing Your Information

Microsoft Outlook stores data in PST (Outlook Data File) or OST (Offline Storage Table) files. Over time, these files can become corrupted due to power failures, abrupt system shutdowns, viruses, or storage issues. When this happens, it’s crucial to repair the file without losing critical information.

This technical article explores advanced methods to recover data from corrupted PST/OST files using Microsoft’s built-in tools and third-party software.

1. Identifying Symptoms of Corruption

Before attempting repairs, recognize common signs of corruption:

• Outlook crashes unexpectedly.
• Error messages such as:
• “The .pst file is not a personal folders file.”
• “Errors were detected in the data file.”
• Missing or duplicated emails, contacts, or calendar entries.
• Extreme slowness when opening Outlook.

2. Methods to Repair a Corrupted PST/OST File

2.1. Using Microsoft’s Built-In Tool (SCANPST.EXE)

Outlook includes the Inbox Repair Tool (SCANPST.EXE) to fix corrupted PST files.

Steps to Run SCANPST.EXE:

1. Locate SCANPST.EXE

• On Windows 10/11, search for:
  C:\Program Files (x86)\Microsoft Office\root\OfficeXX
  (Replace XX with your Office version, e.g., 16 for Office 2016/2019/365).

1. Run SCANPST.EXE

• Open the tool and click Browse to select the corrupted PST file.
• Click Start to begin scanning.

1. Repair the File

• If errors are found, the tool will prompt you to Repair.
• A backup file (filename.bak) is created before applying changes.

1. Open the Repaired File in Outlook

• Go to File > Open & Export > Open Outlook Data File and select the repaired PST.

Note: SCANPST may fail for severely corrupted files. If it doesn’t work, proceed to the next method.

2.2. Using Offline Mode for OST Files

If the issue is with an OST file (used in Exchange/Outlook.com accounts), you can regenerate it:

1. Close Outlook.
2. Go to Control Panel > Mail > Show Profiles.
3. Select the affected profile and click Properties > Email Settings.
4. Disable online sync and restart Outlook in Offline Mode.
5. Outlook will rebuild the OST when reconnected.

2.3. Convert OST to PST (If Outlook Won’t Open)

If the OST is corrupted and Outlook won’t start:

1. Use MFCMAPI (Microsoft Freeware)

• Download from: https://github.com/stephenegriffin/mfcmapi
• Open the OST and export data to a new PST.

1. Use Kernel for OST to PST (Third-Party Tool)

• Professional software that extracts emails, contacts, and calendars from damaged OST files.

2.4. Manual Extraction Using PowerShell (Advanced Method)

For technical users, try extracting data with PowerShell:

Add-Type -Assembly "Microsoft.Office.Interop.Outlook"
$outlook = New-Object -ComObject Outlook.Application
$namespace = $outlook.GetNamespace("MAPI")
$pst = $namespace.AddStore("C:\path\to\corrupt.pst")
$folder = $pst.GetRootFolder()
$items = $folder.Items
$items | Export-CSV "C:\recovered_emails.csv" -NoTypeInformation

Warning: This method requires advanced knowledge and may not work for heavily corrupted files.

3. Third-Party Solutions for Severe Cases

If the above methods fail, professional tools like:

• Stellar Repair for Outlook
• SysTools PST Recovery
• Aryson OST to PST Converter

can recover data from severely damaged files.

4. Preventing Future Corruption

To avoid PST/OST file corruption:

• Back up regularly (use Export to PST in Outlook).
• Avoid oversized PST files (split them if they exceed 10 GB).
• Use stable storage (avoid USB drives or slow networks).
• Keep Outlook and Windows updated to prevent known bugs.

Conclusion

Repairing a corrupted PST/OST file is possible with the right tools. Start with SCANPST.EXE, and if that fails, try MFCMAPI or professional recovery software. Regular backups are key to preventing data loss.

If the file is severely damaged, consult a data recovery specialist to avoid permanent loss.

References:

• Microsoft Support: Repair Outlook Data Files (.pst)
• GitHub MFC-MAPI: https://github.com/stephenegriffin/mfcmapi

This article provides a detailed technical guide for intermediate-to-advanced users. For personalized assistance, consult an IT professional.