One outstanding tool that has amazing features for importing MBOX files to the Office 365 cloud is
eSoftTools MBOX Converter Software. It provides customers with the best tool to import one or more MBOX files to their Office 365 account at once in an intelligent manner. Additionally, it converts MBOX files to a number of other formats with ease, including PST, EML, EMLX, MSG, and more. To learn more about its features, users can import MBOX files with a selection of 25 items to Office 365 using the free demo version.
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Import MBOX files to Office 365 cloud