To restore an OST (Offline Storage Table) file to a Microsoft 365 account, first ensure Outlook is closed. Then, use the Outlook application to import the OST file. Navigate to File > Open & Export > Import/Export, select Import from another program or file, and choose the OST file. Follow the prompts to import the data into your Microsoft 365 account, ensuring all items sync correctly. Finally, verify that all emails, contacts, and calendar items have been restored successfully.

restore OST to Office 365 account

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