There is a plenty of ways to do it and a lot of converters that can help with the process in two clicks, but I recommend the manual method:
- Go to Windows Live Mail (WLM) and open it. Do the same with Microsoft Outlook (MO).
- In WLM, import .eml. To do it, go to File menu, Import, and at last - Import message.
- In WLM, go to File menu, Export and Export Message.
- In the opened window, choose Microsoft Exchange and hit NEXT. This will start the EML to PST conversion process.
- If you did all the operations correctly, you should see a pop-up window about the export process. Click OK to continue.
- Now choose the way to export - all folders or just a selected one.
- OK button will help you convert EML to PST.
- The export process is started and done. Hit Finish.
If you use Microsoft 365 for a big enterprise or a serious organization, you should be aware of the backup tools for SaaS and be always prepared for a recovery process.
Helpful article: https://www.datasciencecentral.com/microsoft-office-365-backup-what-business-data-to-back-up/