If you are still looking for a solution to migrate OST to Office 365, you can download Softaken OST to Office 365 Migration Tool. One feature of the software is that it can easily export the entire OST file and its data items to Office 365, as well as many other email clients like Gmail, Yahoo etc. The software lets you migrate the entire mailbox, public folders, and storage containers. The software works well with all versions of MS Windows including Win 11.