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Outlook Problems · Classic Outlook

ScanPST not working, not responding, or won't recognise the file

If ScanPST.exe hangs, freezes, or throws "does not recognize the file", the usual culprit is a locked file, the wrong path, or a very large PST. Close Outlook, run ScanPST as administrator against the real data-file path, clear the read-only/blocked flags, and give big files time. Here is the accurate, step-by-step fix for classic Outlook on Windows.

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By the 365 Techies team · Reviewed 6 October 2026

Why it happens

Why ScanPST stops responding or won't recognise your file

ScanPST.exe (the Inbox Repair Tool that ships with classic Outlook for Windows) is fussy about three things, and many "not working" reports come down to one of them.

The file is locked. If Outlook is still open in the background - or your antivirus is actively scanning the mailbox file - ScanPST can't get exclusive access, so it hangs at 0% or looks frozen.

You pointed it at the wrong thing. "Microsoft Outlook Inbox Repair tool does not recognize the file" often means you fed it a desktop shortcut, a synced OneDrive placeholder that hasn't fully downloaded, or a path with odd characters - not the real .pst or .ost file. It can also mean the file is too badly corrupted for ScanPST to read at all.

The file is genuinely large. Modern Unicode PSTs can grow to 50GB. ScanPST will still work on them, but it can sit for a long time on one pass and look like it has crashed when it hasn't.

// WINDOWS PCS ONLY

We do not support Outlook on Apple Macs, iPads or iPhones. Apple does not allow our remote-support tool to take control of an iPad or iPhone (an Apple restriction), and our remote support covers Windows PCs only. On an Apple device, Microsoft’s own Outlook help is the place to start.

// FIX IT WITH ME · STEP BY STEP

Fix it with me, one step at a time

The steps from this guide, one at a time, in the order that fixes the most cases fastest. Tell it what happened and it shows the next step. Nothing here leaves your device.Last reviewed 6 October 2026

Checking which Windows you have…STEP 1 OF 6
  1. 01Close Outlook and antivirus

    Fully close Outlook, end any OUTLOOK.EXE process in Task Manager, and pause antivirus that scans the mailbox so the file is released.

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The fix

Fix ScanPST step by step (classic Outlook)

Work through these in order. Nothing here sets out to delete your mail - ScanPST makes a backup copy (a .bak file) before it repairs, though Microsoft notes that items corrupted beyond repair may not be recovered.

  1. Close Outlook completely and pause any antivirus that touches the mailbox. Check Task Manager (Ctrl+Shift+Esc) and end any lingering OUTLOOK.EXE process so the file is fully released.
  2. Find your real data-file path. Reopen Outlook just long enough to go to File > Account Settings > Account Settings > Data Files. Click your file, choose Open File Location, and note the exact folder. Then close Outlook again.
  3. Clear read-only and "blocked". Right-click the .pst/.ost file > Properties. Untick Read-only, and if you see an Unblock tickbox at the bottom (Windows adds this to files copied from the internet or another PC), tick it, then Apply. This is what usually clears the "does not recognize the file" error.
  4. Run ScanPST as administrator. It lives at C:\Program Files\Microsoft Office\root\Office16\SCANPST.EXE for current Microsoft 365 and Office 2016/2019/2021/2024 installs. Right-click it and choose Run as administrator.
  5. Browse to the real file, not a shortcut. Click Browse, paste the exact path from step 2, then Start. Avoid cloud placeholders - if the file lives in OneDrive, make sure it shows the green "Available on this device" tick first.
  6. For very large files, copy locally first. Copy the PST to a plain folder such as C:\PSTFix, run ScanPST against that copy, then place the repaired copy back. This dodges long paths, special characters and sync interference.
  7. Let it finish. On a big mailbox ScanPST can appear frozen mid-scan. Give it time - watch the pass counter rather than assuming it has died - and keep the "Make backup" box ticked so it protects your data before it repairs.

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// GOOD QUESTIONS

Frequently asked

Why does ScanPST say "does not recognize the file"?

Often you've pointed it at a shortcut, a OneDrive placeholder that isn't fully downloaded, or a path with special characters - not the actual .pst/.ost. Copy the real file to a simple local folder like C:\PSTFix, clear the read-only and "blocked" flags in its Properties, then browse to that copy. If it still won't recognise the file after that, the corruption may be beyond ScanPST and the mailbox needs deeper recovery.

ScanPST is not responding - is it frozen or just slow?

On a large mailbox it is usually just slow. ScanPST makes several passes and can sit on one for a long time on a big file, so it looks frozen when it isn't. Make sure Outlook is fully closed and your antivirus isn't scanning the file, then leave it running. If it genuinely hasn't moved after a couple of hours on a huge PST, copy the file to a local folder and try again from there.

Where is ScanPST.exe on my PC?

For current classic Outlook (Microsoft 365, Office 2016/2019/2021/2024) it's normally at C:\Program Files\Microsoft Office\root\Office16\SCANPST.EXE. If you run 32-bit Office on 64-bit Windows, look under C:\Program Files (x86)\ instead. The Office16 folder name is used even on the newest Microsoft 365, so don't be put off by the "16". If you can't find it, search your C: drive for scanpst.exe.

Do I need to run ScanPST as administrator?

It helps. Running it as administrator gives it the permissions to open and rewrite the data file without being blocked, which clears a lot of "won't start" and "can't access" problems. Right-click SCANPST.EXE and choose Run as administrator.

Will repairing the file delete my emails?

Repairing the data file itself doesn't wipe your mail - it fixes the structure and makes a backup copy (a .bak file in the same folder) first, though items corrupted beyond repair may not come back. The one thing to be careful of is an old local POP PST that holds the only copy of your mail; back that up before any repair. For Microsoft 365, IMAP or Outlook.com accounts, everything lives on the server and re-downloads anyway.

ScanPST still won't fix it - what now?

If the file is too badly corrupted, ScanPST bails out or loops. At that point it's specialist recovery, not a retry. We can take a look remotely, salvage what's recoverable and rebuild a clean data file, usually the same day. Call 01202 775566.

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