Email loss has a particular flavour of panic, because it is rarely one file. It is fifteen years of correspondence, invoices, receipts and the one attachment your accountant needs. And Outlook’s data files fail in ways that look catastrophic and often are not.
PST and OST are not the same thing
Getting this wrong sends people down the wrong path for hours.
A PST is a personal storage file. It is the only copy. Historically used for POP accounts, archives and exports. If a PST is lost, the mail is lost with it.
An OST is an offline cache of a server mailbox — Exchange, Microsoft 365, IMAP. The authoritative copy lives on the server. If your OST is corrupted, the usual fix is to delete it and let Outlook rebuild from the server. It is one of the few situations where deleting the broken file is the correct action.
So the first question is always: is this mail on a server somewhere? If it is, stop worrying about the file. If it is a PST, keep reading, and make a copy of it before you do anything else.
Copy the file first
Before any repair tool touches a PST, copy it somewhere else. Repair tools modify the file in place, and a failed repair on your only copy is a bad afternoon. Close Outlook completely first — it holds a lock, and repairing a file Outlook still has open is its own category of problem.
PSTs typically live under your user folder in Documents\\Outlook Files, or in AppData\\Local\\Microsoft\\Outlook. If Outlook still opens, the account settings dialogue will tell you exactly where the file is.
Try Microsoft’s own tool first, because it is free
Outlook ships with a repair utility called ScanPST, installed alongside Office. It is unglamorous and it fixes a good proportion of everyday corruption. It runs multiple passes and you should let it, running it repeatedly until it reports no further errors.
Two known limits: it struggles with badly damaged files, and historically it has been unreliable on very large PSTs. If ScanPST reports success but Outlook still will not open the file, or it crashes partway, you have reached its ceiling.
The file is missing entirely
Different problem, different tool. A deleted PST is an ordinary file recovery job: stop writing to the drive, scan, look for large .pst files. PSTs are big and contiguous enough to recover reasonably well, and their signature is well recognised.
Use EaseUS Data Recovery Wizard, MiniTool Power Data Recovery or another suitable scanner to look for the missing PST or OST. Preserved filenames and folder paths can make several archives easier to identify, but results depend on the file system and what has been overwritten. Check the vendor’s current limits and preview options before paying.
Once recovered, expect to repair as well as recover. A PST pulled off a damaged volume is very often structurally damaged, and that is a repair job, not a recovery one.
When ScanPST is not enough
Dedicated PST repair tools go further than Microsoft’s, chiefly by extracting individual messages from a file that cannot be repaired as a whole and writing them into a fresh PST. That distinction matters: even where the original file is beyond saving, the messages inside it frequently are not.
If a recovered PST will not open, try Microsoft’s built-in Inbox Repair Tool on a copy first. Commercial PST-repair software is a separate category from file recovery, and UrRecover does not currently have a confirmed affiliate relationship for one. Only consider paying for a repair utility when it can preview messages from your specific file.
Routes people forget
- The server, if there is one. Exchange and Microsoft 365 keep recoverable deleted items well beyond what the client shows, often 30 days in a hidden retention area.
- Another device. A phone or laptop still syncing the same account is a complete copy of anything within its sync window.
- The sender. Unglamorous, effective. For a specific critical attachment, asking is faster than any recovery.
- Windows previous versions or Time Machine, if either was running.
Preventing the repeat
- Keep PSTs on local storage, not on a network share. Outlook data files over a network connection are a well-documented source of corruption.
- Split large archives by year rather than growing one enormous file. Smaller files corrupt less and repair more successfully.
- Back up PSTs deliberately. They are frequently missed because they sit in AppData, which many backup tools skip by default.
- Close Outlook properly. A large PST killed mid-write during shutdown is the most common cause of the corruption this article is about.
Short version: work out whether it is a PST or an OST, copy the file before touching it, run ScanPST, and only reach for a paid repair tool once you have seen it preview your actual messages.
Tools for recovering PST and OST files
These are paid-product links from active UrRecover affiliate relationships. Use the free scan or preview first where available, compare what each tool actually finds, and do not buy if the files you need are not visible.
- EaseUS Data Recovery Wizard — Scan for deleted or lost Outlook data files.
- MiniTool Power Data Recovery — A second Windows recovery option for comparison.
- Wondershare Recoverit — Another tracked file-recovery route with preview.
Recovery results depend on the device, the failure and whether new data has overwritten the missing files. Save recovered files to a different drive. For physical damage, unusual noises or an unstable RAID, stop and consult a professional recovery laboratory.
Repairing the mailbox rather than hunting the file
Once you have found the PST or OST, the damage is usually inside it. Stellar Repair for Outlook rebuilds the mailbox structure and lets you preview individual messages before exporting.