Few things are more stressful than opening Outlook after a computer crash, a failed migration, or a dodgy external drive — only to find your backup file won’t open either. If you’ve ever seen an error message when trying to load a .pst or .ost file, you know the sinking feeling. The good news is that a “broken” Outlook backup is very often recoverable, as long as you approach it the right way and don’t make the corruption worse before help arrives.

Here’s a practical, step-by-step guide to recovering emails from a damaged Outlook backup, plus how to make sure you’re never in this position again.

Recover Emails from a Broken Outlook Backup

Why Outlook backup files become corrupted?

Outlook stores your mailbox data locally in one of two file types:

  • PST files — used for local backups, archived folders, and older POP/IMAP accounts.
  • OST files — used for the offline cache of an Exchange or Microsoft 365 mailbox.

Both file types can become corrupted for reasons that are surprisingly common:

  • The computer shut down unexpectedly, or Outlook was closed mid-sync
  • The backup file was stored on a failing hard drive or a USB stick that was removed too early
  • The file exceeded its size limit (older PST files in particular have strict size caps)
  • A sync conflict occurred between OneDrive and Outlook while the file was open
  • Malware or a botched software update interfered with the file structure

Whatever the cause, the result is the same — Outlook throws an error, refuses to open the file, or opens it with folders and emails missing.

Step 1: Stop and don’t overwrite anything

Before attempting any fix, close Outlook completely and avoid running further backups over the damaged file. If your backup lives on an external drive or USB, don’t keep using that device — continuing to write to a failing drive can turn a recoverable file into an unrecoverable one. If you’re not confident about what’s safe to touch, it’s worth getting a professional opinion before you go further; a rushed attempt is one of the most common reasons a recoverable file ends up permanently lost.

Step 2: Try Outlook’s built-in Inbox Repair Tool (ScanPST.exe)

Microsoft includes a free repair utility with every copy of Outlook, called the Inbox Repair Tool (ScanPST.exe). It’s designed specifically to scan and fix structural errors in PST and OST files.

  1. Close Outlook and any other mail-enabled applications.
  2. Locate SCANPST.EXE — it’s usually found in the Outlook installation folder under Program Files.
  3. Open the tool and browse to your damaged PST or OST file.
  4. Click Start to scan. This runs through several internal phases and can take a while for large files.
  5. If errors are found, tick “Make a backup of the scanned file before repairing” — this step is essential, so don’t skip it.
  6. Click Repair, then reopen Outlook once it’s finished.

ScanPST works well for minor corruption, but it has limits. If the tool won’t complete a scan, keeps freezing, or the repaired file still won’t open properly in Outlook, the damage is likely too deep for the built-in tool to handle on its own.

Step 3: Restore from an earlier, healthy backup

If you have an older copy of the PST file that predates the corruption, this is usually the safest and quickest path back to your emails:

  1. Locate your last known good backup file.
  2. Rename or move the corrupted file out of the way (don’t delete it yet, in case recovery is still possible).
  3. Open Outlook and point it to the healthy backup file via File > Open & Export > Open Outlook Data File.

The obvious downside is that anything received after that backup was taken won’t be there. This is exactly why having a proper, automated backup routine — rather than the occasional manual copy — makes such a difference when something eventually goes wrong. If your current setup relies on manual backups, it’s worth reviewing our data backup and recovery service and looking at more reliable options like cloud backup.

Step 4: Rebuild a corrupted Outlook profile

Sometimes the PST or OST file itself is fine, but the Outlook profile pointing to it has become corrupted, which produces the same symptoms as a damaged file.

  1. Close Outlook and open Control Panel > Mail > Show Profiles.
  2. Create a new profile and set it as the default.
  3. Reopen Outlook and reconnect your mail account, or manually add your existing PST file back in.

This won’t help if the underlying file itself is damaged, but it’s a quick way to rule out a profile issue before assuming the worst.

Step 5: When it’s time to bring in a professional

If ScanPST can’t repair the file, no recent backup exists, and a new profile doesn’t solve it, the file is likely dealing with deeper structural corruption — often from a failing drive, an interrupted write, or a size-limit crash. At this point, continuing to experiment with the file yourself risks losing data permanently.

This is where our team can help. We work with damaged PST and OST files regularly and can often recover mailboxes that look completely unopenable, including cases involving:

  • Corrupted files on a failing or dying hard drive
  • Backups interrupted mid-write during a crash or power outage
  • Files affected by a botched Windows or Office update
  • Lost emails needed urgently for insurance claims and reports

If your computer itself is the problem — not starting, freezing, or showing errors — that needs addressing first before any file recovery can safely proceed; our computer repair and data backup recovery teams can work through both together.

How to avoid this happening again?

Once your emails are back, it’s worth putting a proper safety net in place so a single corrupted file never puts years of correspondence at risk again:

  • Move to automated, scheduled backups rather than manual copies you remember to do occasionally.
  • Use cloud backup so your mailbox data isn’t tied to a single physical drive that can fail without warning.
  • Set up a documented disaster recovery plan if you’re running this for a business, so everyone knows what to do — and who to call — if it happens again.

Have a look at our backups and disaster recovery service if you want a proper system in place, or get in touch with our team and we’ll take a look at your damaged file and talk you through your options.