Emails getting caught in "Outbox"

In Outlook for Windows, the Outbox appears when messages are waiting to be sent. If messages are being caught there, use these checks in order:

1. Make sure Outlook is online
   • Go to Send/Receive.
   • If Work Offline is highlighted, select it to turn it off.
   • Then select Send All.
2. Check whether a stuck message has a large attachment
   • A large attachment is a common reason a message stays in the Outbox.
   • Go to Send/Receive > Work Offline.
   • Open Outbox.
   • Delete the stuck message, or drag it to Drafts, open it, and remove the attachment.
   • Turn Work Offline off again.
3. Turn on automatic sending
   • If mail only leaves the Outbox after a manual send/receive, the Send immediately when connected setting may be off.
   • Go to File > Options > Advanced.
   • In Send and receive, enable Send immediately when connected.
   • Select OK.
4. Check Sent Items after sending
   • Sent mail should appear in Sent Items after it is successfully sent.
   • If an item is still in Outbox, it has not been sent yet.
5. If Sent Items seems missing or unusual
   • Expand the folder list and check Sent Items.
   • If mail is not appearing there, Outlook settings may need adjustment.

If the message sends only when pressing F9 or manually using Send/Receive, step 3 is the key fix.

References:

• Outlook email stuck | Microsoft Support
• Email stays in the Outbox folder until you manually initiate a send/receive operation in Outlook
• View sent email | Microsoft Support