The most reliable method of migrating PST files to Office 365 is by using a powerful and trusted tool like Regain PST to Office 365 Migration Tool. It allows you to easily transfer all items in PST files including emails, attachments, calendars, and notes from the Outlook PST file into Office 365 mailboxes within no time. Allows bulk migration without any size restrictions, causing very heavy PST files to be transferred easily. Further, Regain's software retains the structure of folders as well as metadata to provide exact mailbox mapping for seamless migration. Featuring an easy-to-use interface and a demo version offered, it’s the ideal option for a smooth, secure PST to Office 365 transition.