How to resolve the error "The OST file is in use and cannot be accessed"?

webbyravi

If you're getting the error "The OST file is in use and cannot be accessed", it usually means Outlook cannot access the OST file because another process is using it or the file has become corrupted.

Follow some troubleshooting steps:

✔ Close Outlook completely.

✔ Restart your computer to release any file locks that may be preventing access.

✔ Disable antivirus or backup software temporarily, as these applications sometimes lock OST files during scans.

✔ Create a new OST file by closing Outlook, renaming the existing OST file, and reopening Outlook. Outlook will automatically create a fresh OST file and resync mailbox data.

✔ Repair or recreate your Outlook profile through Control Panel > Mail > Show Profiles if the issue persists.

✔ Check file permissions to ensure your user account has full access to the OST file location.

If the OST file is severely damaged or contains unsynchronized data that cannot be accessed, you can use a BLR OST to PST Converter Tool to extract and preserve your mailbox data.

anny12

Those are good troubleshooting steps. I'd also recommend checking whether Outlook processes are still running in the background through Task Manager, even after closing Outlook. Sometimes a lingering OUTLOOK.EXE process can keep the OST file locked and trigger this error.
If recreating the OST file doesn't resolve the issue, the problem could be related to Outlook profile corruption or an inaccessible OST file. In cases where the OST contains important mailbox data that hasn't synchronized with the server, deleting the file may not be the best option.
Before recreating the OST, consider backing it up. If the file becomes inaccessible or Outlook fails to open it, a dedicated solution like Stellar Converter for OST can help extract emails, contacts, calendars, attachments, and other mailbox items from the OST file and save them to PST format. This can be particularly useful when dealing with orphaned OST files or Outlook profile issues.
Also, check available disk space and ensure the OST file isn't stored on a network location, as Microsoft recommends keeping OST files on a local drive for optimal performance and accessibility.