How to repair a damaged PST file with the Inbox Repair Tool (SCANPST)

Signs that a PST file is damaged

Corruption rarely announces itself politely. These are the usual signs:

• Outlook shows a message that errors have been detected in the file and suggests running the Inbox Repair Tool.
• Outlook says the file is not an Outlook data file or cannot be accessed.
• Outlook freezes or crashes when you open a particular folder, or every time it starts.
• Folders appear empty, message counts look wrong, or searches miss mail you know is there.
• Moving or deleting items fails with vague errors.

Not every one of these is corruption. A PST on a network drive, a file still being copied, or a PST that has hit its size limit can produce similar errors. If the file is close to 50 GB, read Outlook PST size limits explained first: a full file just stops accepting new mail and doesn’t need repairing.

PST or OST? Check which file you have

SCANPST is for .pst files: archives, exported mail, POP3 data files and PSTs you opened yourself. Microsoft 365, Outlook.com and Exchange accounts (and, in recent versions of Outlook, IMAP accounts too) use an .ost file instead. An OST is only a local copy of a mailbox that lives on the server.

Microsoft’s advice for a damaged OST is not to repair it but to recreate it: close Outlook, delete (or rename) the .ost file, and start Outlook again. It downloads a fresh copy from the server. Microsoft notes that the Inbox Repair Tool doesn’t scan Exchange mailbox data, so running it on an OST won’t fix your mailbox.

To see which file a folder belongs to, open File → Account Settings → Account Settings in classic Outlook and look at the Data Files tab. It lists each file’s name, type and location. Click Open File Location to jump to it. If you’re unsure about the difference, see OST vs PST.

Where to find SCANPST.EXE

The Inbox Repair Tool is installed with classic Outlook for Windows, but there’s no shortcut to it in the Start menu. You have to open it from the Office program folder. For Outlook 2016, 2019, 2021, 2024 and Microsoft 365, which all use the Office16 folder, it is usually in one of these places:

Most PCs bought in the last few years run 64-bit Office, so try the first folder first. If it isn’t there, check the others, or type scanpst.exe into File Explorer’s search box while you’re in C:\Program Files and C:\Program Files (x86).

Can’t find it anywhere, or it won’t start? Microsoft’s suggestion is to repair Office: in Windows, open Settings → Apps → Installed apps, find Microsoft 365 or Office, choose Modify, and run a Quick Repair (or an Online Repair if that doesn’t help).

How to run the Inbox Repair Tool

1. Close Outlook completely. Check Task Manager for a leftover OUTLOOK.EXE process and end it if necessary; SCANPST can’t work on a file Outlook still has open.
2. Double-click SCANPST.EXE in the folder from the previous section.
3. Click Browse and select the PST. Not sure where it is? The Data Files tab in Account Settings shows the path; by default PSTs live in Documents\Outlook Files.
4. Click Start. The scan runs through several phases and can take from a minute to well over an hour for a large file.
5. If it finds errors, make sure Make backup of scanned file before repairing is ticked, note the backup’s name and location, and click Repair.
6. When it reports Repair complete, run it again on the same file. Microsoft notes the tool may need several passes; repeat until a scan finds no errors.
7. Start Outlook with the profile that uses the repaired file and check your folders.

The Options button lets you choose whether SCANPST writes a log file. Keep it on: the log (a .log file next to the PST) records what was changed or removed.

The .bak file, Recovered Personal Folders and Lost and Found

The backup (.bak) file

With the backup option ticked, SCANPST saves an untouched copy of the original file in the same folder, with the same name and a .bak extension, for example archive.bak next to archive.pst. Don’t delete it until you’re happy with the result.

Recovered Personal Folders and Lost and Found

Usually the repaired PST simply opens as before. When the folder structure itself was damaged, you may instead see a set of folders called Recovered Personal Folders (Inbox, Sent Items, Calendar and so on) and a folder named Lost and Found. Press Ctrl+6 for the Folder List if you can’t see them.

• The recovered default folders are often empty, because they were rebuilt from scratch.
• Lost and Found holds the folders and items the tool rescued but couldn’t put back where they belonged.

Microsoft’s recommended clean-up is:

1. Create a new, empty PST: File → Account Settings → Account Settings → Data Files → Add.
2. Drag the folders and items from Lost and Found into the new PST.
3. Once everything is moved, remove the Recovered Personal Folders file from your profile.

Getting more out of the backup

If items are still missing, you can try to import from the backup. Copy the .bak file, rename the copy with a .pst extension (for example archive-backup.pst), and import it with File → Open & Export → Import/Export → Import from another program or file → Outlook Data File (.pst), choosing Do not import duplicates. The steps are the same as in our PST import guide. Remember the backup is the damaged original, so this often fails; it’s a last attempt, not a guaranteed win.

What SCANPST can’t fix

The Inbox Repair Tool checks the PST’s internal database structures and makes them consistent again. That’s powerful, but it has clear limits:

• It removes what it can’t read. If a block of the file is unreadable, SCANPST deletes it, and any message that depended on it goes with it. The log file lists these removals.
• It can’t bring back permanently deleted mail, or items that were damaged beyond repair.
• It can’t fix a file that is truncated or mostly overwritten, for example one that stopped copying halfway or was replaced by a sync conflict.
• It doesn’t repair OST files or your mailbox on the server. Recreate the OST instead.
• It doesn’t touch a password-protected PST without the password, and it won’t fix problems in Outlook itself, such as a bad add-in or a broken profile.

If SCANPST keeps finding errors or the file won’t open at all, restore the PST from a backup. Third-party recovery tools exist, but results vary, and you’d be trusting them with your entire mail history. Try your backups first.

If the PST came from somewhere else, rebuild it

Many PSTs are copies of mail that still exists elsewhere. Before fighting with a badly damaged file, ask where its contents came from:

• Exported from a Microsoft 365, Outlook.com or IMAP mailbox? If the mailbox still exists, export a fresh PST from it.
• Converted from Gmail, Thunderbird or Apple Mail? If you still have the Google Takeout download or the mbox files, a new conversion produces a clean file. MoveMyInbox doesn’t repair PSTs, but it does create new Unicode PSTs from mbox files, keeping folders, attachments, and read and flagged status.
• The only copy, on one computer? Then the PST is irreplaceable, which is exactly why the next section matters.

If you’re archiving an account you’re about to close, keep the original export as well as the PST. See how to archive an email account before closing it.

How to keep PST files from getting damaged

• Keep PSTs on a local drive. Microsoft says network use of PST files isn’t meant for continuous use, warns that a PST used over a network connection may be corrupted if the connection degrades or fails, and supports networked PSTs only in specific remote-desktop setups.
• Don’t keep an open PST in a synced folder. A PST changes constantly while Outlook is running, which sync apps handle badly. Microsoft notes that OneDrive syncs PST files less often than other files, and publishes instructions for moving a PST out of OneDrive. Dropbox, Google Drive and iCloud Drive face the same basic problem. To back a PST up to the cloud, close Outlook and copy the file.
• Close Outlook properly. Exit Outlook before shutting down, and give it time to finish. Don’t unplug an external drive holding an open PST.
• Watch the size. Large PSTs aren’t corrupt by nature, but they’re slower to open and repair, and more mail is at risk if one goes wrong. Several medium-sized files (per year or per account) are easier to manage than one huge one. Old ANSI PSTs near 2 GB are especially fragile.
• Back up regularly. Copy your PSTs to an external drive or cloud storage while Outlook is closed, and keep more than one generation. A backup is the only fix for a file SCANPST can’t save.
• Compact after big clean-ups. Data File Properties → Advanced → Compact Now reclaims space from deleted items.

Frequently asked questions