I would like to recommend you the best third party solution with the eSoftTools OST to Office 365 Converter software. This tool import outlook OST to office 365 without making any change of original structure. This tool supports all versions of Exchange OST and Outlook.This tool provides to the user various formats to convert OST file into PST, EML, EMLX, Gmail, Office 365, vCard, MBOX, MSG, HTML, etc., if you have any doubt.You can download a free demo file to convert 25 items from each OST file into the Office 365 folder.

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