How to Repair an OST File

An OST (Offline Storage Table) file is used by Microsoft Outlook to store a copy of mailbox information from an Exchange server for offline access. If an OST file gets corrupted, Outlook may have trouble opening or synchronizing it. Here’s how you can attempt to repair an OST file:

1. Use Outlook’s Inbox Repair Tool (Scanpst.exe)

Outlook comes with an Inbox Repair Tool called scanpst.exe that can repair both PST and OST files.

  1. Close Outlook before starting the repair.
  2. Locate the scanpst.exe tool, which is typically found in one of the following locations, depending on your version of Outlook and Windows:

    For Outlook 2019:

    C:\Program Files (x86)\Microsoft Office\root\Office16

    For Outlook 2016:

    C:\Program Files (x86)\Microsoft Office\root\Office16

    For Outlook 2013:

    C:\Program Files (x86)\Microsoft Office\Office15

    For Outlook 2010:

    C:\Program Files (x86)\Microsoft Office\Office14

    For Outlook 2007:

    C:\Program Files (x86)\Microsoft Office\Office12
  3. Run scanpst.exe as an administrator by right-clicking on the file and selecting “Run as administrator.”
  4. Browse to the location of the OST file that you want to repair. This file is typically located in:
  5. Select the OST file and then click Start to begin the scan.
  6. If issues are found, choose to make a backup of the file before repairing and then click Repair.

2. Recreate the OST File

If the Inbox Repair Tool doesn’t fix the issue, you can recreate the OST file by following these steps:

  1. Close Outlook.
  2. Navigate to the OST file location (as mentioned above) and rename the .ost file. For example, change outlook.ost to outlook_old.ost. This ensures Outlook will not use the old file and will create a new one.
  3. Open Outlook again. Outlook will now create a new OST file and re-download the information from the server.

3. Disable Add-ins

Sometimes, Outlook add-ins can cause issues with OST files. You can try disabling them to see if that resolves the issue:

  1. Start Outlook in safe mode by holding the Ctrl key when clicking on the Outlook shortcut or typing outlook /safe in the Run dialog (Win + R).
  2. Go to File > Options > Add-ins.
  3. At the bottom, click on Go next to “Manage: COM Add-ins” and uncheck any enabled add-ins.
  4. Restart Outlook normally and see if the problem persists.

4. Use Outlook’s Built-in Repair Option

For newer versions of Outlook, you can repair the account associated with the OST file:

  1. Go to File > Account Settings > Account Settings.
  2. Select the email account associated with the OST file.
  3. Click on the Repair button and follow the prompts.

5. Check Antivirus Software

Sometimes antivirus software can interfere with Outlook and OST files. Temporarily disable your antivirus to see if it resolves the issue, but remember to re-enable it afterwards.

Important Considerations

  • Backups: Always have a backup of your OST file before attempting repairs.
  • Data Loss: Be aware that some repair processes may lead to data loss. Items that are not synchronized with the Exchange server may be lost when recreating the OST file.
  • Server Data: Remember that the primary data source for an OST file is the server. As long as the server data is intact, you can recreate the OST without data loss.
  • Corruption Causes: If OST file corruption is frequent, investigate the cause, such as disk errors, network issues, or software conflicts.

If these steps do not work, you might need to contact your IT department or seek professional assistance, especially if the OST file is critical and contains data not synchronized with the server.

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