Outlook error 0x8004010f, explained and fixed

Error 0x8004010f is Outlook's object-not-found error. It typically shows up during send and receive with a line such as "The operation failed. An object cannot be found." The missing object is almost always local: the offline address book Outlook tries to download, or the offline data file (OST) that Cached Exchange Mode works from. The mailbox on the server is rarely the problem.

The fix, in order

  1. See which task fails. Press F9 or open Send/Receive Progress and note the exact task in the error text. If only the offline address book task fails, jump to step 4. If every task fails, start at step 2.
  2. Find and check the OST file. In File, Account Settings, Data Files, select the account and open the file location. The OST should be present and roughly the size of the mailbox. A zero-byte or missing OST means Outlook will rebuild it; close Outlook, delete the broken OST, and reopen Outlook so a fresh copy downloads.
  3. Check folder permissions. Right-click the OST, Properties, Security. The Windows account needs full control of the folder it sits in. A profile moved from another PC or restored from backup often carries permissions for an account that no longer matches.
  4. Download the address book manually. Send/Receive tab, Send/Receive Groups, Download Address Book, tick Download changes since last Send/Receive and choose the full details option. If the manual download succeeds, the error was a stale local address book copy.
  5. Turn Cached Exchange Mode off and back on. Account Settings, Change, untick Use Cached Exchange Mode, restart Outlook, then re-enable it and restart again. This forces a clean resync of the offline store.
  6. Create a new Outlook profile. Control Panel, Mail, Show Profiles, Add. Configure the account in the new profile and set it as default. If the error vanishes, the old profile was corrupt; the old OST can be deleted once the new one has synced.

If it still happens

If every machine in an organization gets this error at once, the fault is server-side, usually the offline address book generation or its distribution point, and no amount of local repair will fix it. On a single machine, the profile rebuild in the last step resolves nearly every remaining case.

Common questions

Is 0x8004010f a server error or a local error? Usually local. It is a MAPI object-not-found report raised by Outlook while working with its offline store or the offline address book, which is why the same mailbox often works fine in webmail while Outlook errors.

Will deleting the OST delete my email? No. The OST is a local cache of server data. Deleting it while Outlook is closed simply makes Outlook download a fresh copy on the next start. Mail that exists only locally, such as old PST archives, is a different file and is not touched.

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