Why Do I Have 4 Different Versions of an Outlook .PST in Amazon S3? I'll get back to you on the broader questions you asked, but according to your retention settings you're keeping two versions and you're not removing files from backup storage that have been deleted locally. That's perfectly fine, assuming you understand than any files that are deleted or moved will remain in backup storage indefinitely. Given that it looks like you have two backup locations in storage for that pst, my initial guess is that the file was moved. I believe Microsoft Office did that with the 2016 version, if memory serves. If you want, you can check the option to delete files that have been deleted locally, but I would put a delay in the deletion of at least 14 days or more, to ensure that if the endpoints ever hit by something like ransomware the backups are safe for that minimum amount of time. Or you could just enable that option without a delay and wait for the next plan execution to run and see if the versions that are not needed anymore are removed from backup storage. And then you can turn that option back off.