It doesn’t happen too often but when a message is stuck in the Outbox it can be a real pain. Below you’ll find three methods to get the message out of the Outbox.

Method 1

Open the message from the Outbox and close it again. Now select the message and press DELETE

Method 2

Put Outlook in offline mode. To do this go to File-> Work Offline. Now restart Outlook and see if you can delete it (you can try this in combination with method 1). Don’t forget to put Outlook back On-line again.

Method 3

  1. Create a new pst-file; File-> New-> Outlook Data File…
  2. Set this pst-file as your default delivery location in your Account settings; Tools-> E-mail Accounts-> button Next
  3. When you now restart Outlook your original pst-file will show up as the secondary set of folders where should easily be able to remove the file from or even the complete Outbox folder
  4. Set the original pst-file as the default delivery location again and restart Outlook; the Outbox folder will be recreated and will be empty.

Method 4

Use the Microsoft MDBVU32.EXE tool to forcefully clear the Outbox. The instructions for this are the same for when removing a stuck read receipt but instead of choosing “MDB-> Open Root Folder” choose “MDB-> Open IPM Outbox”.

Some Knowlegde base articles about this subject in case the problem still persists;
KB291613: Sent Messages Remain in Your Outbox
KB293031: Message Copy Remains in the Outbox When You Send Through a Hotmail or IMAP Account While Offline
KB311001: You Cannot Send Messages if There Are More Than One Thousand Messages in Your OST Outbox
KB293038: A Copy of a Forwarded Message Stays in the Outbox
KB195922: OL2000: How to Troubleshoot Mail Stuck in the Outbox