Start with Microsoft’s free ScanPST.exe (Inbox Repair Tool) for minor corruption find it at C:\Program Files\Microsoft Office\root\Office16, browse to your PST file and click Repair. If ScanPST fails or the file is over 2 GB with severe damage, import recoverable items into a new PST file using Outlook’s Import/Export wizard. If the file won’t open at all, use Univik PST Converter to extract emails directly to EML, MBOX or PDF without needing the PST to be healthy first.
Outlook won’t open. Or it opens but one folder is completely empty. Or you get an error that says the data file cannot be accessed.
That is a corrupt PST file. And it happens more often than it should oversized files, abrupt shutdowns, bad sectors on the hard drive or an antivirus scanner locking the file mid-write. Any of these can leave a PST in a state where Outlook cannot read it.
The good news: most PST corruption is recoverable. This guide walks through the three repair methods in the right order, starting with Microsoft’s free tool and moving to stronger options when that isn’t enough.
Signs Your PST File Is Corrupt
Before going further: if Outlook runs fine in Safe Mode (hold Ctrl while clicking the Outlook icon) but fails normally, the issue is likely a corrupt add-in not the PST file itself. Disable add-ins first and retest. Only proceed with PST repair if the problem persists in Safe Mode too.
Why PST Files Get Corrupted
Oversized File
ANSI-format PST files (Outlook 2002 and earlier) hard-limit at 2 GB. Unicode PST files (Outlook 2003+) have a theoretical 50 GB limit but become unstable in practice beyond 20 GB.
Improper Shutdown
Closing Outlook by force-quitting, powering off mid-sync or a system crash while Outlook is writing data leaves the PST in an inconsistent state.
Bad Sectors
A failing hard drive, a USB drive with physical damage or a network share with connectivity issues during a write operation all cause data corruption in the PST file.
Antivirus Interference
Some antivirus tools scan PST files mid-write and lock them. The interrupted write leaves the file header or index in a broken state.
Before You Run Any Repair Tool
Do this before touching the PST file. It takes two minutes and protects you if a repair attempt makes things worse.
Close Outlook completely. Check Task Manager and confirm OUTLOOK.EXE is not running. ScanPST and any repair tool requires exclusive access to the PST file. If Outlook is open, the tool will either fail or produce incomplete results.
Make a copy of the PST file first. Navigate to the file in File Explorer and copy it to a different folder or drive. Name it something like outlook-backup-before-repair.pst. If a repair attempt corrupts the file further, you still have the original state to work from.
Note the file size. Right-click the PST file and check Properties. Files under 2 GB: ScanPST will handle them. Files between 2 GB and 10 GB: ScanPST may work but may need multiple passes. Files over 10 GB with severe corruption: consider Method 3 directly.
Method 1: ScanPST.exe Microsoft’s Free Inbox Repair Tool
ScanPST.exe is the right first step for most PST corruption. It comes installed with every copy of Outlook and costs nothing. It works by scanning the file’s internal structure for inconsistencies and rebuilding corrupted index entries.
Where to Find ScanPST
The tool is not in the Start menu. You need to find it in the Office installation folder. The path depends on your Outlook version and whether you have the 32-bit or 64-bit version installed.
| Outlook Version | ScanPST.exe Location (64-bit) |
|---|---|
| Outlook 2021 / 2019 | C:\Program Files\Microsoft Office\root\Office16 |
| Outlook 2016 | C:\Program Files\Microsoft Office\root\Office16 |
| Outlook 2013 | C:\Program Files\Microsoft Office 15\root\Office15 |
| Outlook 2010 | C:\Program Files\Microsoft Office\Office14 |
If you have the 32-bit version of Outlook installed on a 64-bit Windows machine, replace Program Files with Program Files (x86) in the path above. The fastest way to find it on any version is to open File Explorer and search for scanpst.exe in the search bar.
Running the Repair
Double-click scanpst.exe to open the Inbox Repair Tool dialog. Click Browse and navigate to your PST file. The default PST location is %localappdata%\Microsoft\Outlook paste this into the File Explorer address bar to go there directly.
Click Start. ScanPST runs through 8 phases, analysing the file header, folder tree, message database, attachment blocks and other internal structures. On a 1 GB PST file this takes 2 to 5 minutes. Larger files take proportionally longer.
If errors are found, click Details to see what ScanPST found (though the details are often minimal). Check the box to Make a backup of the scanned file before repairing this creates a .bak file alongside the original. Then click Repair.
After repair completes, click OK and then run ScanPST again on the same file. Repeat until the scan reports no errors. Severely damaged files often require 3 to 5 passes before all errors are cleared.
Open Outlook. Check the folder list for a folder called Recovered Personal Folders or Lost and Found. Any items ScanPST recovered that it could not place in the original folder structure appear here. Drag them to the correct folders manually.
What ScanPST Cannot Fix
ScanPST is a surface-level repair tool. It rebuilds the index and fixes structural inconsistencies but it has hard limits.
Severely corrupted data blocks. ScanPST can rebuild the folder structure but cannot recover email content from data blocks that are physically damaged. Those items are simply gone from ScanPST’s perspective.
Very large files with deep corruption. Files over 5 to 10 GB with widespread damage cause ScanPST to time out or crash without completing the repair. The tool was designed for smaller personal mailboxes.
Encrypted or password-protected PST files. ScanPST cannot read inside an encrypted PST file. It will report the file as corrupt when in reality it simply cannot decrypt the content.
Permanently deleted items. If emails were deleted from the Deleted Items folder before the corruption happened, ScanPST will not recover them. That data was already gone before the damage occurred.
Method 2: Import Into a New PST File
If ScanPST repaired the file but some folders are still empty or inaccessible, try pulling the recoverable content into a fresh PST file. This bypasses the damaged areas of the original file and captures everything that is still intact.
Open Outlook. Go to File then Open and Export then Import/Export. Choose Import from another program or file and click Next.
Select Outlook Data File (.pst) and click Next. Browse to the corrupt PST file. Select Do not import duplicates and click Next.
Choose the destination folder. Check Include subfolders. Click Finish. Outlook imports every email it can read from the corrupt file into the current mailbox. Items in areas of the file that are too damaged to read are skipped.
This method works well when the PST is partially readable ScanPST fixed the structure but some individual message blocks remain damaged. The Import/Export wizard simply skips over whatever it cannot open rather than stopping entirely.
Method 3: Extract Emails With Univik PST Converter
When ScanPST fails and Outlook cannot open the PST file at all, you need a tool that reads the PST format directly bypassing Outlook entirely and extracting every email it can reach from the raw file structure.
Univik PST Converter reads PST files at the structural level without requiring Outlook to be installed or functional. It accesses the internal message database, extracts emails folder by folder and saves them to formats you can actually use MBOX for re-importing into any mail client, EML for individual message access or PDF for permanent compliance archiving.
What Univik PST Converter Does
- Reads PST files without Outlook installed
- Extracts readable emails from partially corrupt files
- Skips unreadable blocks and continues rather than stopping
- Preserves original folder hierarchy, timestamps and attachments
- Converts to MBOX, EML, MSG or PDF in batch
- Generates a conversion report showing what was extracted
- 100% offline your PST file never leaves your machine
When to Use It
- ScanPST completed but emails are still missing
- Outlook won’t open the PST file at all
- The PST is over 5 GB and ScanPST keeps crashing
- You need a PDF archive of emails for legal or compliance purposes
- You are migrating away from Outlook and want MBOX output for Gmail or Thunderbird
- You need the file repaired urgently and cannot wait for multiple ScanPST passes
Univik PST Converter
Load a corrupt or inaccessible PST file and extract every readable email to MBOX, EML, MSG or PDF. Works without Outlook installed. Handles large files. Preserves folder structure and original timestamps. Generates a full extraction report. 100% offline.
✓ Works on corrupt files
✓ MBOX, EML, MSG, PDF output
✓ Full extraction report
✓ 100% offline for Windows
Which Method Should You Use?
| Situation | Start With |
|---|---|
| Outlook throws a corruption error but the file is under 2 GB | ScanPST run until it reports no errors |
| ScanPST repaired but some folders are still empty | Method 2 Import into a new PST file |
| PST file is over 5 GB and ScanPST crashes or won’t complete | Univik PST Converter directly |
| Outlook won’t open the file at all, not even partially | Univik PST Converter directly |
| You need PDF output for compliance or legal hold | Univik PST Converter (PDF output mode) |
| Migrating to Google Workspace and need MBOX from a corrupt archive | Univik PST Converter (MBOX output) |
If you are using a corrupt PST as part of an Outlook to Google Workspace migration, see our Outlook to Google Workspace migration guide for the full workflow. A corrupt PST file is the most common blocker in that process.
Preventing PST Corruption
Keep PST files under 10 GB. Use Outlook’s Auto-Archive (File then Tools then Clean Up Old Items) to move messages older than 12 months to a separate archive PST. This keeps your active file small and stable.
Never store PST files on a network drive or USB stick. IOPS latency over a network share and the risk of USB disconnection mid-write are the two most reliable ways to corrupt a PST file. Store it on local SSD or a well-maintained HDD only.
Close Outlook properly before shutting down. File then Exit. Wait for Outlook to fully close before restarting or powering off the machine. Force-killing OUTLOOK.EXE during a sync is one of the primary causes of corruption.
Exclude PST files from real-time antivirus scanning. Add the Outlook data file folder (%localappdata%\Microsoft\Outlook) to your antivirus exclusions list. Antivirus real-time scanning of a PST file mid-write has been a documented cause of corruption for over a decade.
Back up PST files regularly. Copy the PST to a separate drive (or cloud backup) at least weekly. If corruption happens, your worst case is losing one week of email rather than years of data.
Frequently Asked Questions
How many times do I need to run ScanPST?
Run it until it reports no errors. Moderately corrupted files typically take 2 to 4 passes. After each pass that finds and repairs errors, run it again from scratch. Once a scan completes with no errors found, the repair is done. If ScanPST still finds errors after 6 or more passes, the damage is too severe for it to fix fully and you should move to Method 2 or 3.
My PST file is 20 GB. Will ScanPST work on it?
ScanPST may work but frequently crashes or stops mid-scan on files this large with significant corruption. If ScanPST cannot complete its scan, use Univik PST Converter directly. It reads the PST structure at a lower level than ScanPST and does not have the same failure behaviour with large files.
Can I recover permanently deleted emails from a corrupt PST?
If the emails were deleted before the corruption happened, no tool can reliably recover them the data was already overwritten. If emails disappeared because of the corruption (they existed before the PST broke), both ScanPST and Univik PST Converter may recover them depending on the degree of damage to those specific message blocks.
ScanPST says the file has been repaired but emails are still missing. Why?
ScanPST repaired the file structure but the individual message blocks for those emails were damaged beyond recovery. The folder exists but the emails inside it are gone from ScanPST’s perspective. Try Method 2 (importing into a new PST) to see if Outlook can pull those messages from the raw file. If that also fails, those emails are likely unrecoverable through ScanPST.
Do I need Outlook installed to use Univik PST Converter?
No. Univik PST Converter reads PST files directly without Outlook. This matters when you need to recover emails from a machine where Outlook is not installed or when Outlook itself will not open due to profile corruption linked to the damaged PST.
Where is my PST file located?
In Outlook, go to File then Account Settings then Account Settings. Click the Data Files tab. The path to each PST file is listed there. The default location is %localappdata%\Microsoft\Outlook paste this into the File Explorer address bar to navigate there directly.
Conclusion
Last updated: May 2026. ScanPST.exe steps verified against Microsoft’s official documentation and tested on Outlook 2019 and 2021. PST size limits from Microsoft’s published specifications for ANSI and Unicode PST formats.
PST corruption looks catastrophic but is usually recoverable. ScanPST handles the majority of cases. When it doesn’t, importing into a new PST file rescues the readable content. When neither works, a converter that reads the file structure directly extracts what’s left.
The one mistake worth avoiding: trying to repair a PST file without a backup copy first. Make the copy, then work on the original. That 30-second step has saved a lot of people from a very bad day.
Has ScanPST worked for you in the past or have you had to go further to recover a badly corrupted archive?