If you are looking for the best software to upload OST to Office 365, then I would recommend eSoftTools OST to PST Converter software. This software is capable of breaking large OST files into smaller PST files with just a few simple steps. Moreover, users get a preview option in this smart tool, allowing you to see the preview before conversion. So, try it now without any delay.

Read more- https://www.esofttools.com/blog/upload-ost-to-office-365-without-outlook/