Outlook error 0x80040600, explained and fixed

0x80040600 is Outlook's unknown error, which makes it unhelpful as a diagnosis but consistent in practice: when Outlook cannot name the failure, the cause is usually damage in the local data file (PST or OST) or in the profile that points at it. It tends to appear on send and receive, on opening folders, or when deleting mail, often right after a crash, a forced shutdown, or a data file growing very large.

The fix, in order

  1. Run the Inbox Repair Tool. Close Outlook and run scanpst.exe, found in the Office installation folder. Browse to the PST or OST shown under File, Account Settings, Data Files, scan, and let it repair. Take the backup it offers. Run it again until it reports no errors, up to a few passes.
  2. For an OST, skip repair and rebuild instead. An OST is a cache. Close Outlook, rename or delete the OST, and reopen Outlook; a fresh copy syncs from the server. This is faster and more reliable than repairing a cache file.
  3. Check the file size. Unicode PST files have a default limit of 50 GB in current Outlook versions, and old ANSI-format PST files cap at 2 GB and corrupt easily near it. A file near its limit needs compacting after deleting and emptying Deleted Items, or archiving into a second file.
  4. Isolate add-ins. Run outlook /safe. If the error stops, disable COM add-ins in batches under File, Options, Add-ins. A failing add-in can surface as this generic code because Outlook cannot attribute the crash properly.
  5. Create a new profile. Control Panel, Mail, Show Profiles, Add. Connect the account and the existing data file to the new profile. If the error stays behind in the old profile, profile corruption was the cause.
  6. Repair Office itself last. Settings, Apps, Microsoft Office, Modify, Quick Repair first and Online Repair if needed. This replaces damaged program files without touching data.

If it still happens

If scanpst reports errors it cannot repair and the file keeps growing worse, recover what is readable by creating a new PST and moving folders into it in small batches, skipping the folder where the move fails. That folder holds the corruption; the rest of the mail is usually intact.

Common questions

Is 0x80040600 a virus? No. It is a generic failure code, and its common causes are a damaged data file, an oversized data file, or a corrupt profile. Malware is not on the usual list for this code.

What is the difference between repairing a PST and an OST? A PST holds the only copy of its mail, so it is worth repairing carefully with scanpst. An OST is a disposable cache of server mail, so deleting and resyncing it is both safer and quicker.

Related errors

Outlook error 0x8004010f · Outlook not responding · Word file is corrupted