There are two possible methods available for migrating the OST file to Office 365. The first is the manual process importing OST to Office 365 via the PST file. It means the first conversion of OST to PST is required and then from PST to Office 365 is possible. Taking care of the time there is various software in the market to minimize the duration and the complexity of the manual process. One such solution is MailsDaddy OST to Office 365 Migration Tool that helps to upload OST data to Office 365.