Hidden in the same folder as your broken PST there may be a file with a .bak extension - the state of your mailbox just before the repair. Used correctly, it is an undo button.
When you tick Make backup of scanned file before repairing, ScanPST quietly saves a snapshot of the file before it changes anything, in the same folder, with the same name and a .bak extension. Most users never notice it exists - until a repair completes and the result is worse: folders missing, Outlook unhappy, mail gone that the broken file still showed. That is the moment the .bak earns its keep. It is not magic and it has one sharp limit, explained below - but as a way back to the pre-repair state, nothing else is as fast.
The .bak is a snapshot of the working copy, taken immediately before that repair pass began. Two consequences follow. First, it exists only if the backup checkbox was ticked - one more reason that checkbox is a habit, not an option. Second, it is refreshed on every pass: after three passes, the .bak holds the state before pass three, not the state before pass one. Your separate File Explorer copy of the original remains the only true "before everything" version.
In each case the goal is the same: treat the .bak as a source to recover mail from, or as a cleaner starting point - not as a finished mailbox.
The .bak might be your only copy of that state, so handle it like an original:
.bak file to a safe folder first - never rename the only .bak in place.bak to .pst (if extensions are hidden, turn on File name extensions in Explorer's View menu so the rename is real, not cosmetic)With the recovered file open beside your working PST, copy folders or individual items across by drag and drop, or use Import/Export to bring selected folders in. Expect possible duplicates if the repaired file also contains some of the same items - duplicates are a nuisance, missing mail is a loss, so accept the nuisance.
Work folder by folder and verify as you go: counts, a few spot-checked messages with attachments, and the date range ends. When everything you need is across, close the recovered file and keep it stored until you are certain nothing else is wanted from it.
No .bak means the checkbox was off, and the pre-repair state survives only in your File Explorer copy of the original - which is why the copy-first rule outranks every other habit in this series. If neither exists, your remaining materials are the repaired file itself and whatever an extraction tool can carve from it. State it plainly because it is the lesson that prevents the next incident: one repair without a copy is a gamble; the same repair with two backups is a procedure.
Watch the video to see the repair side of the story - then check your own folder for the .bak most users never knew they had.
Watch Full VideoUsually the rename was not real because Windows was hiding file extensions, so the file still ends in .bak behind the scenes - or the file was renamed while Outlook still had the folder open. Show file name extensions, confirm the file truly ends in .pst, and open it from a fresh profile.
Not necessarily. The BAK mirrors the working copy at that moment - if you had already run passes on that copy, earlier drops are already baked in. Compare against your untouched original copy to see the truest before-state you have.
You can attach it and work, but the BAK is the pre-repair - meaning still corrupt - state. Use it as a source to copy mail out of, or repair a copy of it; do not promote it to your daily file as it stands.