If you have bulk OST files on the local system and want to seek a professional technique to import OST files to Office 365 without any data loss I recommended to make use of an automated process which is DailySoft OST To Office 365 Migrator is a reliable solution for both personal and professional purpose based on advanced technology that does effortless tasks in a few seconds once user upload OST file the scanning technology sans all OST data in a few seconds the software takes users Office 365 login details for importing process the software ensures while importing process they can't do any annotations on it the application is compatible with all versions of windows and offers demo version user must try it without paying anything. 

Do you need to import offline OST files in Office 365? Then, you can try OST to PST Converter software - a correct and well-developed application for users to accurately import offline OST files in Office 365 with complete data contacts and attachments. It can migrate your bulk items from OST file to Office 365 in a single process without missing a single piece of detail. To learn more about this tool, you can first use its trial edition which is compatible with migrating the first 25 items from OST to PST free of cost. After using its trial edition, you can go with the licensed edition of the tool to import offline OST files in Office 365.