If you are using Outlook 2011 for Mac, use one of the following methods to delete messages stuck in your Outbox.
When the message is stuck because it has a large attachment:
- Right click on message in outbox, choose “open message”
- Remove the attachment
- Press send
This will re-send the message without the over-sized attachment. If you don't want to send the message, delete it from the outbox.
If you don't want to send the message or its stuck for other reason, try this method:
Close Outlook 2011, hold the shift button down while reopening Outlook. Go to outbox and delete the “stuck” message.
The Outbox is not visible
If the Outbox is not visible, initiate a send and receive and open the Progress dialog. Click the little x at the right of the entry to stop the progress. The Outbox should now be visible in message list and you can remove the attachments or delete the message.
Windows users, see Delete a message stuck in Outlook's Outbox
Email is stuck in the Outbox in Outlook for Mac 2011 (MSKB)