Outlook Not Sending Email
Emails sit in the Outbox without sending, or sending fails with an error message, while receiving mail may still work normally.
Quick answer: Emails stuck in the Outbox are usually stuck on a connection problem or an oversized attachment, rather than anything wrong with the recipient's address. Check the Outbox for a specific error message first — it usually points directly at the cause.
Likely causes
- A temporary connection issue between Outlook and the mail server
- An attachment that's too large for the mail server's limits
- An outdated or incorrect outgoing (SMTP) server setting, particularly after changing providers
- The account requiring re-authentication
What you can safely check yourself
- Open the Outbox and check for a specific error message attached to the stuck email
- Check the attachment size if the email includes files
- Try sending a short test email with no attachment to isolate whether it's an attachment-specific issue
- Send/Receive manually (F9) to force Outlook to retry
When it needs a proper look
If a simple test email without attachments also gets stuck, that points to an account or server setting issue rather than the specific email — worth getting help to check the account setup.