For a free way to import PST files to Office 365, Microsoft’s native PST Import is the first option that you can try; this manual way works well when you only have a few PST files.

The problem comes with the manual method. You need Microsoft 365 admin permissions, upload the PST files to Microsoft’s import location, prepare the CSV mapping that tells Microsoft which PST goes to which mailbox, and then create the import job. For a few files that is manageable, but with dozens of PSTs it becomes repetitive and easy to mis-map a mailbox.

When I had to move several old PST archives into Microsoft 365, I wanted a simpler way to review the data before importing it. I ended up checking TrustVare PST to Office 365 Converter because it could read the PST directly, preview the mailbox, let me select the required folders, and transfer the selected data to Office 365. That was useful when I didn’t want to import an entire archive blindly.

So, for a couple of PST files, Microsoft’s free import route is enough. For multiple archives or selective PST migration, a direct PST to Microsoft 365 tool can save a lot of the manual handling.

You can convert multiple EML files into a single PST using a standalone tool like TrustVare EML to PST Converter. For a few EML file conversions, you can use the manual method, but it becomes hard and time-consuming when you have large files, so it does not guarantee accurate migration. So my preferred choice is to use a reliable utility like this. This software supports features like bulk processing, preview option, selective conversion, and accurate conversion. I also used this tool for email to PST export; it preserved all information accurately.