Fix ScanPST Repair Error

Work on a Copy of the PST, Never on the Original

Close Outlook completely, then open Task Manager and confirm OUTLOOK.EXE is no longer running — a PST that is still open does not copy cleanly. Find the file's location in Outlook under File → Account Settings → Data Files, then copy the PST in File Explorer (ideally onto a different drive) and check in Properties that the copy's size matches the original exactly. From here on, ScanPST only ever touches the copy.

Find ScanPST and Start the Scan the Clean Way

ScanPST — the Inbox Repair Tool — is installed with Outlook but hidden. For Microsoft 365 and Outlook 2021 / 2019 / 2016 with the normal Click-to-Run install, it sits here:

C:\Program Files\Microsoft Office\root\Office16\SCANPST.EXE

If your Office is 32-bit, use the same path under Program Files (x86) instead. Older versions swap the last folder: Office15 for Outlook 2013, Office14 for Outlook 2010. Double-click SCANPST.EXE, use Browse to select your copy of the PST, and click Start. The scan runs through 8 phases and reports what it found. Keep the working copy on a local disk, not a network path, and make sure Outlook stays closed. If the scan completes and offers a Repair button, take it — that is the happy path. The next steps are for when it does not.

Decode the Error Message Before Retrying Anything

Each ScanPST failure message points at a different cause, and each one has a different cure — retrying blindly wastes the file's remaining readable data. The three messages that matter:

"An error has occurred which caused the scan to be stopped. No changes have been made to the scanned file." The structure is badly damaged, or something interfered mid-scan — Outlook still running, an antivirus scanning the file, or a failing disk. The reassuring half is true: nothing was written, so the file is exactly as it was. Rule out interference and retry once on the clean setup; if it stops at the same phase every time, the damage at that spot is real.

"The Inbox Repair Tool does not recognize the file" (or "not a personal folders file"). The header itself is destroyed, or the file is not really a PST at all — check that the size is not 0 KB and the extension is genuinely .pst. Repeat passes cannot help a file the tool cannot even identify.

Fatal Error 80040818. The classic signature of an old ANSI-format PST that has hit its 2 GB wall (corruption in ANSI files typically begins around 1.8 GB). No repair pass can fix a format limit — the honest route is conversion into a modern Unicode PST.

Run Repeat Passes the Way They Are Meant to Run

One pass rarely finishes a badly damaged PST, and that is documented behaviour, not a trick: ScanPST fixes the top layer of errors, which lets the next scan walk deeper into the file and find the next layer. The correct rhythm: scan, note the error count, then repair — with Make backup of scanned file before repairing ticked, so ScanPST saves a .bak snapshot of the working copy before the pass. Immediately scan the same working copy again, and keep going while the error count keeps falling — three to five passes on a genuinely damaged file is normal.

Stop when a full scan reports no errors, or only minor inconsistencies. The warning sign is a count that stops changing: two identical results in a row mean this tool has reached its limit on this file, and more passes only rewrite it for nothing.

When ScanPST Reaches Its Limit — the Honest Ladder

When ScanPST has done all it can, climb in this order. Roll back one pass: if a repair made things worse, rename a copy of the .bak file to .pst and you are back to the pre-repair state. Import route: if the repaired file scans clean but Outlook still refuses it, create a fresh profile with a brand-new PST and import the repaired file's folders into it. Extraction tools: paid third-party tools rebuild a new PST from the damaged one and often rescue items ScanPST dropped — judge them by a free preview, never by promises. Restore from backup: if you have one, it beats every repair ever written.