Error 0x8004010F ("Outlook data file cannot be accessed" or sometimes "The operation failed. An object could not be found.") shows up when Outlook tries to send or receive email but can't properly reach the PST or OST file your profile is supposed to be using.
Common causes
- The data file was moved or renamed. If your PST file was relocated (manually, by a backup tool, or during a migration) and Outlook's profile still points to the old path, this breaks the link.
- A corrupted Outlook profile. The profile is what manages the connection between your account settings and the data file — over time, this can become damaged independent of the data file itself.
- A corrupted PST/OST file. Sudden Outlook closures, crashes, or interrupted syncs can damage the data file directly.
- The PST file is stored inside a OneDrive-synced folder. OneDrive can grab a lock on the file while syncing, conflicting with Outlook's need for exclusive access — this is the same underlying mechanism behind a separate, more severe Outlook-OneDrive conflict introduced in a January 2026 Windows update, but this error code can show up from the same general cause independent of that specific update too.
- Mismatched Offline Address Book (OAB). If the OAB cached on your machine doesn't match the version on the mail server, Outlook can fail to correctly resolve contact/account details, triggering this error.
Fix 1: re-download the Offline Address Book
Worth trying first since it's quick and low-risk:
- In Outlook, go to Send/Receive tab
- Click Download Address Book
- Check the box for Download changes since last Send/Receive
- Click OK, let it complete, then close and reopen Outlook
- Try sending an email to check if the error is resolved
Fix 2: locate your data file and create a new profile
If the address book refresh didn't help, this is Microsoft's own recommended fix for this error:
- Open Control Panel → Mail (you can search "Mail" directly in Windows search if Control Panel's classic view is hard to find)
- Click Show Profiles
- Select your current profile and click Properties → Data Files
- Note down the exact name and file path of your current data file(s)
- Close this window, then click Add (back in the profile list) to create a brand new profile
- Set up the new profile, and when prompted for a data file, point it to the existing PST/OST file you noted down — don't create a new blank one, since your existing emails live in the file you already have
- Set the new profile as default, then restart Outlook
Your data is safe through this process — creating a new profile doesn't delete or touch your existing PST/OST file. You're just rebuilding the connection between Outlook's settings and the data file, which is often enough to clear up a corrupted profile without losing anything.
Fix 3: if the data file itself is corrupted
If the above doesn't resolve it, the PST/OST file itself may be damaged:
- For a PST file (typically POP3 accounts): use Microsoft's built-in Inbox Repair Tool (SCANPST.EXE), usually found in your Office installation folder (commonly under
C:\Program Files\Microsoft Office\root\Office16, though the exact path varies by Office version). - For an OST file (IMAP, Exchange, or Microsoft 365 accounts): the OST is just a local cached copy of your mailbox, so the safer fix is usually to close Outlook, rename or delete the OST file, then reopen Outlook — it will automatically rebuild a fresh OST by re-syncing from the server.
If the file is stored inside OneDrive
If your PST/OST currently lives inside a folder OneDrive is actively syncing, moving it to a purely local folder (outside any cloud-sync folder) resolves the underlying file-locking conflict permanently, rather than needing to repeat any of the above fixes each time it recurs.