Hello,
importing OST files directly is not supported and we do not plan to have this option in the future.
OST files are primarily meant for offline storage of data to later synchronize with the server. As such, data in a single file could be incomplete.
However, if you choose the option to Import data from Microsoft Outlook>Import whole accounts , the data will be loaded from both PST and OST files available.
Regards,
Olivia