Quick answer
PST and OST file errors are usually resolved by running the built-in `scanpst.exe` tool for PST files, or by creating a new profile or resyncing for OST files. Always make a copy of the file before any repair. If the error recurs, the cause may be a damaged disk or an oversized file.
How to recognize the problem
- Outlook displays a message that the data file is corrupted or cannot be opened
- The program crashes or freezes when opening email
- Messages, folders, or contacts are missing after a restart
- Error 0x8004010F or a similar code appears when sending and receiving
- Outlook prompts to run a check on the data file
Most common causes
Corruption due to improper shutdown
If the computer is turned off or Outlook is forcibly closed during a write, the PST or OST file may become corrupted. Power outages can also cause corruption.
Oversized data file
Older-format PST files (ANSI) have a 2 GB limit, and even newer files can slow down performance when they are huge. Outlook may report an error when the file exceeds the recommended size.
Bad disk or network interruption
Bad sectors on the disk or a connection loss to the Exchange server can leave the OST file in an inconsistent state. Synchronization then reports an error.
Faulty profile or add-in
Rarely, the problem is caused by the Outlook profile itself or an add-in that modifies the data file. In that case, repairing the file does not help until the cause is removed.
Step-by-step fix
- 1
Make a copy of the data file
First open Outlook and locate the file: go to
File > Account Settings > Account Settings, thenData Filesand note the path. Then close Outlook and copy the.pstor.ostfile to another location or an external disk. This preserves your data if the repair fails. - 2
Run the PST file check tool
The
scanpst.exetool comes with Outlook. Look for it in the folderC:\Program Files\Microsoft Office\root\Office16(or a similar path for your version). Run it, clickBrowseand select the PST file. Before you clickStart, in the options select to make a backup, then run the check. - 3
Repeat the check until errors are gone
After the first repair, the tool may report that there are still errors. Run it again until it says the file is correct. If errors keep coming back, the file is probably seriously damaged; check the disk and add-ins (step 6), and if it is a PST, finally import the data from the backup (step 7).
- 4
For OST files, create a new profile
The OST file is a cache of an Exchange or Microsoft 365 account and is not repaired directly. Go to
Control Panel > Mail > Show Profiles > Addand create a new profile with the same account. Outlook will download the data from the server again. You can remove the old profile once you are sure everything works and synchronization is complete. - 5
Rebuild the OST file
If you do not want a new profile, close Outlook and rename the existing
.ostfile (add.oldto the end). Start Outlook; it will create a new OST and synchronize your email. Do this only if the account is Exchange or Microsoft 365 and all data is synchronized with the server, because locally unsynchronized items may be lost. - 6
Check the disk and disable add-ins
Open
Command Promptas administrator and first runchkdsk C: /scan, which only checks the disk. If the tool reports errors, back up important data and only then runchkdsk C: /f(on the system disk it will require a restart). Then in Outlook go toFile > Options > Add-insand disable suspicious add-ins. If the error goes away, re-enable add-ins one by one to find the culprit. - 7
Restore data from backup
If the PST file is unrepairable, import the copy:
File > Open & Export > Import/Export > Import from another program or file > Outlook Data File (.pst). Select the backup file and the folder you want. After import, check that messages and contacts are in place. Note that only data that was in the copy will be restored.
When the problem is deeper than the file
If the error returns even after a new profile and repair, the cause is probably hardware or the account itself. Check disk health with the manufacturer's tool (e.g., Samsung Magician or Western Digital Dashboard) and look in Event Viewer > Windows Logs > System for disk errors. For a Microsoft 365 account, check whether the mailbox on the server is accessible via webmail; if everything works there, the problem is local. Split large PST files (over 20 GB) into several smaller ones or switch to an Exchange/IMAP account where email is stored on the server. Regularly back up the PST file to an external disk, because repair does not always restore all data.
How to prevent it
- Always close Outlook before shutting down the computer and wait for the program to exit
- Make a weekly backup of the PST file to another disk or the cloud
- Keep the PST file under 20 GB and archive old messages
- Regularly update Outlook and Windows with patches
When to call a professional
If the error recurs even after repair and a new profile, or if there are signs of disk failure, it is better to contact IT support. They can check the hardware, save the data, and if necessary restore the account on the server.
IT infrastructure maintenance · Servers, networks, backup, security and helpdeskFAQ
Can repairing a PST file delete messages?
The `scanpst.exe` tool makes a backup before repair if you select that option, but in rare cases it may remove corrupted parts. Therefore, first manually copy the file to a safe place.
Can I repair an OST file with the same tool?
No, `scanpst.exe` works only with PST files. OST is resolved by creating a new profile or renaming the file so that Outlook creates a new one and downloads email from the server again. Before that, make a copy and check that all data is synchronized, because locally unsynchronized items may be lost.
What does error 0x8004010F mean?
It indicates that Outlook cannot access the data folder, often due to a corrupted profile or PST/OST file. A new profile or file repair will help, depending on the account type.