How to Repair a Corrupted Outlook OST File

To repair a corrupted Outlook Offline Storage Table (.ost) file, you can recreate the file or use Microsoft’s built-in repair utility.

Method 1: Recreate the OST File (Recommended & Easiest)

Because .ost files are just a synced offline cache of your mailbox on the server, deleting or renaming a damaged .ost file safely forces Outlook to automatically rebuild a fresh copy.

1. Close Outlook completely.
2. Press Windows Key + R, type the following path, and press Enter:
   C:\Users\%username%\AppData\Local\Microsoft\Outlook\
3. Locate your .ost file, right-click it, and rename it (e.g., add .old to the end) or delete it.
4. Restart Microsoft Outlook. Outlook will automatically generate a new .ost file and re-download your emails, calendars, and contacts from the server. (Ensure you have a stable internet connection).

Method 2: Use the Inbox Repair Tool (SCANPST.EXE)

If you need to scan a specific data file, note that Microsoft’s built-in SCANPST.EXE is primarily designed for .pst files, though it can scan local data file structures.

1. Exit Outlook.
2. Open File Explorer and navigate to your Microsoft Office installation folder (typically found at C:\Program Files\Microsoft Office\root\Office16 or C:\Program Files (x86)\Microsoft Office\root\Office16).
3. Double-click SCANPST.EXE to launch the Inbox Repair tool.
4. Click Browse to select your .ost (or .pst) data file.
5. Click Start to begin scanning for errors.
6. If errors are detected, click Repair.

Note: For severely damaged Exchange-backed .ost files, Microsoft officially recommends Method 1 (deleting the .ost file to let it re-sync) rather than running ScanPST.

If you are running into a specific error message or if your account is not an Exchange/Office 365 mailbox, let me know the exact Outlook version or error code so I can narrow down the fix.

Credit By : Webstation