Outlook Error 0x8004010F: Data File Cannot Be Accessed

Outlook error 0x8004010F stops your inbox cold, and the message it surfaces — 'The data file cannot be accessed' — tells you almost nothing useful. Two completely different problems produce this exact code: an Offline Address Book that failed to download in an Exchange or Microsoft 365 environment, and an Outlook mail profile that can no longer find the PST or OST file it was pointed at. The repairs are entirely different. Apply the OAB fix to a missing data file and you waste an hour without changing anything. Apply the data-file fix to an OAB error and you risk pointing Outlook at the wrong archive.

This guide explains what the error code literally means, gives you a causes table so you can confirm which situation you are in, and walks through each repair procedure in order. Identify your variant first; then go directly to the relevant fix.

What does Outlook error 0x8004010F mean?#

The hex code 0x8004010F maps to the MAPI error MAPI_E_NOT_FOUND — Outlook tried to reach a resource it expected to exist and found nothing where it expected something. The code is generic: the same value gets raised regardless of which resource is missing.

In practice, the code surfaces in two separate situations. The first is an Offline Address Book failure. When Outlook is connected to an Exchange server or Microsoft 365, it periodically downloads a local copy of the company directory called the Offline Address Book (OAB). If that download fails — due to a server permission problem, a stale OAB generation, or a corrupted local cache — Outlook reports 0x8004010F inside the Send/Receive dialog, often with a line referencing the OAB or address book download.

The second situation is a broken data file link. Outlook stores email in a PST file for local accounts, or an OST file for Exchange and Microsoft 365 accounts running in cached mode. When the mail profile was created, it was pointed at a specific path on disk. If that file was moved, renamed, deleted, or lives on a network share that is no longer connected, the profile cannot find it and throws 0x8004010F. This variant appears on Outlook startup or the moment you click a folder inside the missing file.

Both situations produce the same error code. The accompanying text in the dialog and the context in which it appears — Send/Receive progress window versus startup or folder click — is usually enough to separate them before you start any repair.

Causes of 0x8004010F: confirm before you fix#

Use this table to identify your cause. The 'How to confirm' column is the critical step — it tells you which scenario you are actually in before you run a repair procedure.

Fix 1: Reset the Offline Address Book#

This fix applies when the error appears in the Send/Receive dialog and the text references the Offline Address Book. The procedure clears the corrupted local OAB cache and forces a fresh download from the Exchange server.

1. 1

   Close Outlook completely

   Quit Outlook. Check the Windows system tray to confirm there is no Outlook process still running in the background. If there is, right-click the icon and choose Exit.

2. 2

   Delete the local OAB cache folder

   Open File Explorer and navigate to C:\Users\[YourName]\AppData\Local\Microsoft\Outlook\Offline Address Books. Delete every subfolder inside that directory. These are cached files — Outlook recreates them automatically. If AppData is hidden, enable 'Hidden items' under File Explorer's View menu first.

3. 3

   Reopen Outlook

   Launch Outlook. It detects that the OAB cache is empty and begins a fresh download automatically. Watch the Send/Receive progress indicator in the status bar.

4. 4

   Force a manual download if it does not start

   Go to the Send/Receive tab in the ribbon, click Send/Receive Groups, then Download Address Book. In the dialog, select Full Details and click OK. The download progress appears in the Send/Receive dialog.

5. 5

   Confirm the error is resolved

   Run a manual send/receive with F9. If 0x8004010F no longer appears in the progress window, the OAB cache was the cause and the repair is complete.

Fix 2: Reconnect or recreate the data file#

This fix applies when the error appears on startup or when clicking a folder, and the error text shows a file path ending in .pst or .ost. The goal is to point Outlook at a file that actually exists — either by locating the original or removing the broken reference and creating a new one.

1. 1

   Find the current data file path

   If you copied the full error text, you already have the path. If not: go to File in the ribbon, then Info, then Account Settings, then Account Settings again. Click the Data Files tab. Every data file attached to the current profile is listed with its full path on disk.

2. 2

   Check whether the file still exists

   Open File Explorer and navigate to the listed path. If the file is there but on a network drive, reconnect the drive and relaunch Outlook. If the file has been moved to a different folder, note its new location before continuing.

3. 3

   Update the path if the file was moved

   In the Data Files tab, select the broken entry and click Open File Location to browse for the file in its new location. If the dialog does not allow editing, click Remove to detach the broken reference, then Add to attach the file from its new path.

4. 4

   Create a new data file if the original is gone

   If the PST was deleted or is unrecoverable, go to File, then New, then Outlook Data File. Name the file and save it to a stable local path such as Documents\Outlook Files — not a network share that might disconnect. In account settings, set it as the default delivery location.

5. 5

   Restart Outlook and verify

   Close and reopen Outlook. The startup error should be gone. If the missing file contained local-only mail, check the Recycle Bin and any backup location before concluding that data is lost.

Fix 3: Rebuild the Outlook profile#

A profile rebuild is the fix for persistent errors that survive Fix 1 and Fix 2, or for corruption that affects multiple Outlook functions at once. A fresh profile does not carry the broken references of the old one.

1. 1

   Open Mail in Control Panel

   Press the Windows key, type Control Panel, and open it. Search for Mail. On Windows 11 you may need to switch to Small Icons view to find it. Click Show Profiles.

2. 2

   Add a new profile

   Click Add, give the profile a name, and follow the account setup wizard. Enter your email address and let Outlook auto-discover server settings. For Microsoft 365 or Exchange accounts this usually completes without requiring manual server configuration.

3. 3

   Connect existing data files if present

   After the profile is created, go to Account Settings then Data Files and add your existing PST file if it is on disk. Do not re-add an OST file for a cached Exchange or Microsoft 365 account — OST files regenerate automatically from the server when the new profile connects.

4. 4

   Set the new profile as default

   In the Show Profiles dialog, select 'Always use this profile' and choose the new profile from the dropdown. Click OK.

5. 5

   Launch Outlook with the new profile and test

   Open Outlook. It should connect cleanly. Run a send/receive and click through several folders to confirm 0x8004010F does not reappear. If it does, the cause is server-side rather than profile-side — contact your Exchange or Microsoft 365 administrator.

How to tell which cause you have before you start#

The causes table maps the symptoms to the fix, but here is the practical shortcut: look at when and where the error appears.

If it appears inside the Send/Receive progress dialog while Outlook is otherwise running normally, and the accompanying text mentions the address book or OAB, start with Fix 1. You can open folders, read and compose mail — the OAB download is failing, not the profile itself.

If it appears on Outlook startup before you can do anything, or when you click a specific folder, and the error text shows a file path ending in .pst or .ost, start with Fix 2. Outlook is trying to open a file that is not at the path the profile recorded.

If you have already run Fix 1 or Fix 2 and the error returned within the same session or on the next launch, or if multiple Outlook features are broken simultaneously, the profile is likely corrupted deeply enough to require a rebuild. Go directly to Fix 3.

How to prevent Outlook error 0x8004010F from coming back#

Most recurrences come from the same two root causes. For the OAB variant: keep the Exchange OAB generation schedule healthy on the server side, and avoid aggressive antivirus scans of the Outlook cache folder, which can corrupt OAB files mid-download. For the data-file variant: keep PST files on stable local storage rather than network shares, and never move or rename a PST while Outlook is closed without updating the profile path immediately after.

For both variants, keeping the Outlook profile lean reduces the risk: remove data file links that are no longer needed, and do not let PST files grow past a few gigabytes without splitting them. Large, fragmented PST files are significantly more prone to the corrupted headers that produce this error.

If your organization uses Exchange, verified OAB regeneration schedules and correctly configured download virtual directory permissions prevent the server-side cause from recurring. An Exchange or Microsoft 365 administrator can set OAB regeneration to run daily and monitor OAB health from the Exchange Admin Center.

Error 0x8004010F is a symptom of a structural fragility: Outlook profiles track data file locations by an exact path on disk, and any environment change — a new machine, a moved folder, a disconnected network drive — can silently break the link. We build AI Emaily, an AI-native email client that keeps mail synced server-side across Gmail, Outlook, and other providers without depending on local PST or OST file paths. The 'data file not found' class of error does not apply to that architecture. AI Emaily does not replace Outlook for organizations locked to Exchange, but for individuals and teams who want to stop managing data file paths and just have their inbox work reliably across devices, the difference in approach is worth knowing about.