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:
- Make sure Outlook is online
- Go to Send/Receive.
- If Work Offline is highlighted, select it to turn it off.
- Then select Send All.
- 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.
- 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.
- 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.
- 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.
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