backup problem

Firstly, regarding missing emails, the background info you provided mentions instances where PST data disappeared for others. It's good that you're reaching out for help. Now, let's explore a few steps to troubleshoot and hopefully resolve this issue.

Consider checking if the 'AutoArchive' feature is turned on. Sometimes, Outlook automatically moves older items to an archive folder. Verify if your missing emails ended up there. PST file corruption could be another culprit. The 'Inbox Repair Tool' in Outlook might help, but for severe cases, you could try a tool like Stellar Repair for Outlook. It's known for effectively handling large-sized PSTs with accuracy and speed.

Hidden folders can sometimes play hide and seek. Open Control Panel, go to File Explorer Options, and unhide folders as described in the steps. It might reveal the missing data. Improper view settings can cause items to disappear. Check if any filters are applied to your view settings. Click on View Settings from the View menu and then Filter to investigate.

Given the complexity of the issue, trying out different solutions might be beneficial. You've got various options to explore, from unhiding folders to repairing PST files.