Import PST Files to Office 365 Importing a PST file to Office 365 means transferring old Outlook emails, folders and attachments to an Office 365 mailbox. It is possible, but how you do it depends on whether you have Outlook installed and how much data you need to migrate.

For a simple manual technique, do the following:
  • Launch Outlook and add the Office 365 account.
  • Click File > Open & Export > Import/Export.
  • Select Import from another program or file. Choose the PST file.
  • Choose the folders you want, and then finish the import.
  • Check the mailbox in Office 365 to verify the emails and attachments are present.

In case Outlook is not available or if you need to move large PST files, then you can rely on Gaintools PST to Office 365 Converter as an offline tool. It helps you to import PST data directly into Office 365 with folder structure and attachments retained.
It is better to verify the migration results with a demo version before you process the complete mailbox data.