If you want to migrate OST file into Outlook 365, I recommend using the eSoftTools Best OST to PST Converter Free program. It has the ability to convert an OST file without having to install MS Outlook. There are no file size limits with this program, and you can convert unlimited OST file data of OST files to PST without losing any records. It can transfer OST files into Yahoo, Gmail, Zimbra, Office 365, ICS, HTML, and more.
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