Outlook and PST “Corruption”

Microsoft Outlook is still a popular email app, used by companies across the world, and home users like myself.

But it seems like Microsoft 365 editions of Outlook have an annoying habit of complaining that a user’s PST file is corrupt and refusing to start. You’re directed to use the SCANPST tool, which says it fixed the errors… but Outlook soon starts complaining about it being corrupt again. But IS IT really corrupt? Is all your data just… gone?

Maybe… but probably not. One habit I picked up from an old timer somewhere along the way (and that refuses to die) is that you’re supposed to run SCANPST on a PST file repeatedly (sending the backups to the Recycle Bin, just in case), until the tool says “only minor inconsistencies were found in this file”:

Outlook SCANPST window

In my version of SCANPST, the “Repair” button is even greyed out, so I couldn’t even run it if I wanted to. So you don’t run the tool once. You run it 3-4, maybe even 5 times, until you see the screen above.

Anyway, if you’ve run SCANPST several times, and you’re sure your hard drive\SSD isn’t failing (by running chkdksk for example, or getting S.M.A.R.T. warnings, or corrupted files in other apps) then chances are Outlook has just gotten stuck in panic mode and needs help getting out of it:

Shut down Outlook, then open REGEDIT and navigate to

HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\PST

You may wish to back up this key for safety. Once that’s done, delete the LastCorruptStore and PromptRepair keys. Open Outlook… and everything should be OK now.