We already tried the Outlook method, but the import stopped with an error about an unsupported attachment file type. Unfortunately, it didn’t tell us which file or email was causing the problem.

We tried to find the source of the error, but couldn’t identify it. That’s why we’re now looking for professional software that can log every detail during the import process and help us identify any problematic files.

Thanks!

Can you not just do it from Outlook https://learn.microsoft.com/en-us/previous-versions/troubleshoot/outlook/how-to-manage-pst-files

Once its there it will populate to O365 cloud so when you login to OWA of that email account its there.

try this

https://www.mailsdaddy.com/pst-to-office-365-migration-tool/

I have never used it but good reviews about it