Quick answer
If Outlook shows an error like “The Outlook data file cannot be accessed” (or similar messages about PST/OST files), the problem is usually one of these: a corrupted data file, wrong file permissions, a damaged Outlook profile, antivirus interference, or a misplaced default data file. Below are six practical, step-by-step fixes you can try. Back up your files before you start.
Before you begin — safe preparation
1) Close Outlook. 2) Locate and copy your PST/OST file to a safe folder (external drive or another folder). Typical locations: %LOCALAPPDATA%MicrosoftOutlook or %USERPROFILE%DocumentsOutlook Files. 3) Make sure Windows has a recent system restore point or a full backup if the mailbox is critical.
Why this error happens (brief)
Outlook’s data files (.pst for POP/Archive, .ost for Exchange/IMAP cached copies) can become inaccessible when they’re corrupted, locked by another process, moved, or when the current Windows user lacks file ownership or permission. Antivirus software, disk errors, or a faulty Office installation can also cause the same symptom.
6 fixes that resolve the problem
1. Repair Microsoft Office
Often the simplest fix is to repair Office. This resets components Outlook depends on without deleting your email files.
Steps: Control Panel > Programs > Programs and Features > select Microsoft Office > Change > choose Quick Repair first. If that fails, run Online Repair (requires internet). Restart your PC and reopen Outlook.
2. Run the Inbox Repair Tool (scanpst.exe)
Microsoft includes the Inbox Repair Tool (scanpst.exe) to repair corrupted PST files. Locate scanpst.exe (it lives in your Office installation folder), run it, point it to the PST file, and follow the prompts. After repair, start Outlook and check if the error is gone. If you have an OST; you can delete the OST (after confirming mail is on the server) and let Outlook recreate it.
3. Create a new Outlook profile
Corrupt profiles cause many access errors. Creating a new profile forces Outlook to build fresh settings and, for IMAP/Exchange/Office 365 accounts, a new OST cache.
Steps: Control Panel > Mail > Show Profiles > Add. Create the new profile, add your account(s), and set the new profile as default (Always use this profile). If the new profile fixes the error, you can import needed data from the old PST copy.
4. Check and set the Inbox/Deliver folder and default data file
If Outlook is set to deliver mail to a non-existent folder or the default data file is missing, you can get an access error. In Outlook: File > Account Settings > Account Settings > Data Files tab — confirm the listed file exists and is set as Default if appropriate. If not, add the correct file and choose Set as Default, then restart Outlook.
5. Verify file ownership and permissions
If Windows doesn’t let Outlook open the PST/OST, you may need to take ownership and grant full control to your user account.
Steps: In File Explorer right-click the PST/OST > Properties > Security > Advanced > change Owner to your user account (or Administrators). Then ensure your user has Full control. Apply changes and reopen Outlook. If you recently restored files from another PC or external source, permissions are a common culprit.
6. Create a new data file (or move it) and set as default
If the existing PST is badly damaged or stored on a problematic drive, create a new PST and set it as the default delivery location.
Steps: File > Account Settings > Account Settings > Data Files > Add > create a new Outlook Data File (.pst). Select it and click Set as Default. Restart Outlook and import the old PST contents (File > Open & Export > Import/Export). Always keep a copy of the original PST until you’re sure everything works.
Other checks that frequently help
- Temporarily disable antivirus or real-time scanner to check for conflicts (re-enable after the test).
- Run chkdsk on the drive where your PST/OST is stored to rule out disk errors.
- Install Windows and Office updates — sometimes a patch resolves compatibility issues.
- Open Outlook as Administrator (right-click > Run as administrator) for a quick permission test.
When to contact support or use a recovery tool
If the PST is heavily corrupted and scanpst can’t fix it, you have two reasonable options: use a professional Outlook recovery tool or contact your IT support. If this is a corporate mailbox on Exchange/Office 365, your administrator can reapply mailbox settings or recreate the mailbox on the server. If you recently had a repair or file restore performed, make sure file permissions and ownership were set correctly — guidance on securing the system after service can be helpful.
Additional resources
If you encounter similar access problems in other desktop programs (for example, when a business application cannot open its data file), see our step-by-step troubleshooting guide on fixing app file access errors in other software such as QuickBooks.
FAQ
Q: Can I safely delete the OST file?
A: Yes — if your mailbox is on an Exchange, Office 365 or IMAP server, Outlook will rebuild the OST automatically. Back up the file first if you are unsure.
Q: Will Office repair delete my emails?
No. Repairing Office replaces program files and fixes components; it doesn’t delete PST/OST data. Still, make a backup before major troubleshooting.
Q: What if none of these steps work?
At that point, consider a commercial PST recovery service or contact Microsoft support or your IT department. If mail is hosted online, your admin may be able to re-provision the mailbox so you can recreate the local cache without data loss.
Following these steps resolves the majority of “data file can’t be accessed” errors. Start with the non-destructive options (backup, repair, scanpst) and move to permissions and profile rebuilds if needed.
