To repair corrupted OST file in Outlook, you can first try Microsoft’s built-in Inbox Repair Tool (ScanPST.exe). Close Outlook, run ScanPST, select the OST file, and start the repair process. However, if the OST file is severely damaged or ScanPST fails, using a professional OST repair tool is the best option. Advanced tools can safely repair corrupted OST files and recover emails, contacts, calendars, and attachments without any data loss.