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1Clear out junk files and repair common Windows errors2Scan for outdated or missing drivers - takes under a minute3Repair Windows errors before they cause bigger problemsIf Outlook can’t open a data file or the set of folders, first check whether the file is a PST or an Exchange OST. Back up a PST, then use Microsoft’s Inbox Repair Tool, SCANPST.EXE, to scan and repair it. An Exchange OST is an offline mailbox cache that Outlook can recreate; it is not repaired the same way.
Identify whether the file is a PST or an Exchange OST
In classic Outlook, go to File > Account Settings > Account Settings > Data Files. The list shows the data files and their associated accounts. This distinction matters: a PST can contain local Outlook data and is the file you scan with Inbox Repair, while an Exchange OST is an offline cache of mailbox data.
| File type | What to do | What Inbox Repair checks |
|---|---|---|
| PST | Back it up, then scan and repair the selected file with SCANPST.EXE. | Errors in that local Outlook data file. |
| Exchange OST | Outlook can recreate the offline cache when it opens again. | Inbox Repair does not connect to or analyze data stored in the Exchange mailbox. |
See Microsoft’s instructions for repairing Outlook data files for the file-type distinction and repair details.
Repair a PST with SCANPST.EXE
Microsoft’s guidance applies to Outlook for Microsoft 365, Outlook 2024, Outlook 2021, Outlook 2019, and Outlook 2016. Close Outlook before running the tool.
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- Close Outlook. Make sure the application is no longer open.
- Make a separate copy of the PST. Keep the original backup in a safe location before attempting repair. Microsoft recommends backing up the existing file first.
- Find and run SCANPST.EXE. This is the Inbox Repair Tool included with Office. Browse to the PST you want to check and start the scan. The location varies by Office installation; Microsoft gives
C:Program Files (x86)Microsoft OfficerootOffice16as a location example for Outlook 2019 and Outlook 2016, not as a universal path. - Repair detected errors. If the scan reports errors, choose Repair. Microsoft notes that you may need to run the tool more than once.
- Reopen Outlook using the associated profile. Check the repaired file for recovered content, including the Recovered Personal Folders and Lost and Found folders. Some reconstructed folders may be empty.
The tool checks the selected local data file and offers to fix detected corruption; it is not a service that repairs or searches the contents of an Exchange mailbox.
If Outlook uses an Exchange OST
An Exchange OST is an offline cache, rather than the mailbox itself. Microsoft says Outlook can recreate the OST the next time Outlook opens after it is deleted. The mailbox data remains on Exchange; Inbox Repair does not inspect or repair that server-side data. If you are unsure whether a file is an OST or PST, check its account association under File > Account Settings > Account Settings > Data Files before taking action.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What to expect from a repair—and what to do if it fails
Look for recovered items
Inbox Repair may place reconstructed content in Lost and Found under Recovered Personal Folders. Some recovered folders may be empty, and Microsoft warns that items permanently deleted or corrupted beyond repair may not be recovered.
Keep the repair backup if you need to search for more items
By default, the repair process creates a backup file with a .bak extension beside the original. If the repaired PST opens, you can make a copy of that backup, rename the copy with a .pst extension, and import it into Outlook to look for additional recoverable items. Preserve the original backup while doing this.
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Separate data-file errors from Outlook startup or freezing problems
If Outlook still freezes or will not start after the data-file repair, the cause may be an Office application or profile problem rather than file corruption. Microsoft’s separate guidance for classic Outlook not responding, stuck at Processing, or freezing recommends considering Office repair or creating a new Outlook profile. Those steps address application or profile issues; they do not necessarily repair a damaged PST.
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