Outlook stores their mailbox data in two file formats OST & PST. If you an Outlook user want to convert your OST data files to Office 365 email client directly then, I recommend you to opt for the professional software solution. the manual method of
conversion is a bit lengthy and there is a major risk of data loss.
For More Info Follow this blog:
https://www.cigatisolutions.com/blog/import-ost-file-into-office-365/
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