Microsoft Outlook — Error 0x8004010F — What It Means & How to Fix It

What Does This Error Mean?

Error 0x8004010F means Outlook cannot access your data file — the file where your emails, contacts, and calendar are stored. Outlook knows where the file is supposed to be, but either it has moved, been renamed, or the path to it is broken. This error is very common after a Windows profile change, a OneDrive sync issue, or after moving Outlook to a new computer. You do not need to reinstall Outlook — you just need to point it to the correct data file.

Affected Models

Microsoft Outlook 2016
Microsoft Outlook 2019
Microsoft Outlook 2021
Microsoft 365 Outlook

Common Causes

The Outlook data file (.pst or .ost) has been moved, renamed, or deleted
A Windows profile change or new user account broke the path Outlook stored for the data file
OneDrive moved the Documents folder to a cloud location, taking the data file with it
The data file is stored on a network drive that is not currently connected
A recent Windows Update or Outlook update reset the data file location setting

How to Fix It

Open Outlook and go to File > Account Settings > Account Settings. Click the Data Files tab. You will see your data file listed with a path. Note whether the path looks correct — it should point to a real folder on your computer.

If the path shows a folder that does not exist or a OneDrive path that has changed, that is the problem.
Use Windows File Explorer to search for your data file. Press Windows + E to open File Explorer, then search for *.pst or *.ost in the search box (top right). Wait for results — the file may be in your Documents folder, AppData, or OneDrive.

The AppData folder is hidden by default. In File Explorer, go to View > Show > Hidden items to make it visible.
Once you find the data file, go back to Outlook's Account Settings > Data Files tab. Select the broken entry and click Remove. Then click Add, browse to the data file you just found, and select it.

Do not worry — removing the entry from the list does not delete the file. You are just updating the pointer.
If your data file is in OneDrive and you want to keep it there, make sure OneDrive is fully synced before opening Outlook. The file must be fully downloaded locally — not just a cloud placeholder — for Outlook to use it.

A cloud-only OneDrive file shows a blue cloud icon instead of a green tick. Right-click it and choose Always keep on this device to force a local download.
As a last resort, create a new Outlook profile. Go to Control Panel > Mail > Show Profiles > Add. Set up the new profile with your email account. This creates a fresh data file. Afterwards, you can import your old .pst file via File > Open & Export > Import/Export.

Creating a new profile is a clean-slate option. Your old emails are not lost — you can import the old .pst file into the new profile.

When to Call a Professional

This error does not mean your emails are deleted — the data file still exists, it just needs to be reconnected. If you have searched and cannot find the .pst or .ost file anywhere, or if Outlook crashes when you try to open the data file, contact Microsoft Support or an IT technician. Do not attempt to create a new Outlook profile until you have located the data file — creating a new profile without reconnecting the old file can make your old emails harder to recover.

Frequently Asked Questions

Will I lose my emails if I fix this error?

No — your emails are stored in the data file, and fixing this error is about reconnecting Outlook to that file, not deleting it. As long as you locate the .pst or .ost file before making changes, your emails are safe. Always make a copy of the data file before doing any repairs, just to be safe.

Why did this error suddenly appear? I did not change anything.

Windows updates, OneDrive sync changes, and automatic folder redirections can silently move files without you realizing. A Windows Update that changes OneDrive settings is one of the most common triggers for this error appearing 'out of nowhere'. Outlook remembers a specific path to the data file — if anything moves that file, even automatically, the error appears.

I cannot find any .pst or .ost file on my computer. Where did it go?

The most likely places are: your OneDrive folder (check online at onedrive.com), the hidden AppData folder, or an external drive if you used one. Enable hidden files in File Explorer (View > Show > Hidden items) and search the whole computer. If you have a Microsoft 365 account, your email may also be stored on Microsoft's servers — in that case, the .ost file is just a local cache and can be deleted and re-created safely.