- Load Outlook.
- Put Outlook in offline mode (File -> Work Offline: enable).
- Exit Outlook.
- Load Outlook in its safe mode ("outlook.exe /safe"). This ensures no
plug-ins get loaded when Outlook is loaded. Reloading Outlook in
offline mode means it won't touch the stuck item. If Outlook ever
touches the item, you cannot delete it.
- Delete the stuck item in the Outbox folder.
- Put Outlook in online mode (File -> Work Offline: disable).
- Exit Outlook.
- Reload Outlook.