If you want to import OST to office 365 account by using any third party OST to office 365 migration tool, you should try few easy KDETools OST to office 365 converter software. It is a sophisticated utility that enables the user to access emails, attachments, contacts, journals, calendars, notes, drafts, sent items, etc. of inaccessible OST files. Though the OST to office 365 tool you can simply upload single & many OST files to office 365 account , There are few built-in features in Outlook client which you can use here, such as Archive, Export OST to office 365 account ,PST, Live Exchange server, Gmail, OLM, NSF, EMLX, vCal, vCard, EML, MSG, HTML, Zimbra, PDF, MBOX, and etc.. Also, you can use Drag & Drop feature of Outlook. works all MS outlook windows versions such as: - 97 to 2016..