If an email is stuck in your Outbox, it can stop everything else from sending as well. You may only have one bad message, but it can make the whole mail app feel broken.
This is a common email problem, especially in Outlook. A message gets stuck, keeps trying to send, and will not leave the Outbox. Sometimes it is caused by a large attachment. Sometimes Outlook is offline. Sometimes the message itself is damaged or the account is no longer authenticating properly.
If the issue feels more Outlook-specific, see my article on Outlook not sending emails but receiving works.
The frustrating part is that the email may look almost normal. It sits there saying it is sending, but nothing actually moves.
Why an Email Gets Stuck in the Outbox
An Outbox is a temporary holding area for messages that are waiting to send. Normally, an email only stays there briefly before it is handed to the mail server.
When something interrupts that process, the message can remain stuck. Depending on the cause, it may also block every message behind it.
- 📎 The attachment is too large for the mail service.
- 📤 One message is damaged and cannot be sent or deleted normally.
- 🔌 Outlook or the mail app is working offline.
- 🔐 The account password or authentication has failed.
- ⚙️ The sending server settings are wrong or no longer accepted.
- 🧱 A mail profile, add-in, or data file problem is blocking the send process.
One Bad Email Can Block the Queue
One of the most common causes is a single email that has gone wrong. It may have a large attachment, a corrupted file, an invalid recipient, or some other problem that prevents it from sending.
When that happens, the mail app may keep retrying the same stuck message instead of moving on cleanly. This can make it look like all email sending is broken, even though the real issue is one message sitting in the Outbox.
In some cases, the stuck email can be deleted normally. In others, Outlook needs to be taken offline first, restarted, or opened in a way that stops the message from trying to send while it is being removed.
Large Attachments Are a Common Cause
If the stuck email includes photos, scans, PDFs, videos, or several attachments, size is a likely culprit.
Many mail services have attachment limits. Even when a message appears to attach successfully, the sending server may reject it later. Outlook may then keep retrying the message and leave it trapped in the Outbox.
For large files, it is often better to send a cloud sharing link instead of attaching the file directly. That keeps the email smaller and avoids the Outbox getting jammed by one oversized message.
Outlook Offline Mode Can Catch People Out
Outlook has a Work Offline mode. When this is enabled, emails may sit in the Outbox because Outlook is deliberately not connecting to send or receive mail.
This can happen accidentally, especially if someone has clicked the option while troubleshooting another problem. It can also appear after connection problems, profile issues, or Outlook being interrupted during a send and receive cycle.
If Outlook says it is disconnected or working offline, the stuck email may not be the real problem. The app may simply not be connecting properly.
Do Not Keep Pressing Send
When an email is stuck sending, it is tempting to keep clicking Send/Receive or to keep creating new copies of the same email. That can make the problem worse.
You may end up with duplicate messages, multiple stuck items, or several copies being sent later when the problem finally clears.
A safer approach is to stop the queue, identify the stuck message, then decide whether it should be resent, recreated, or deleted.
When the Email Will Not Delete
Sometimes the stuck email cannot be deleted because Outlook is actively trying to send it. You may click Delete and nothing happens, or Outlook may say the message has already started sending.
That usually means the sending process needs to be interrupted before the message can be removed. Depending on the situation, that might involve working offline, restarting Outlook, temporarily disconnecting from the internet, or opening Outlook in safe mode.
The aim is not just to force-delete things randomly. The aim is to remove the blockage without damaging the rest of the mailbox or losing important mail.
When It Is Not Just the Outbox
An email stuck in the Outbox can also be a symptom of a broader sending problem.
If every new message gets stuck, or if the same account will not send from Outlook, a phone, and webmail, the issue may be with the account or mail server rather than one bad email.
In that case, it may need proper troubleshooting across the device, app, account settings, authentication, and server behaviour. For broader help with this type of problem, see my main emails not sending page.
What I Check When Fixing a Stuck Outbox
When I troubleshoot this problem, I do not just delete the message and hope for the best. I check where the sending process is failing so it does not immediately happen again.
- ✅ Whether the stuck message is the only problem or part of a larger sending failure.
- ✅ Whether Outlook is online, connected, and using the correct account.
- ✅ Whether attachments are too large or causing the message to stall.
- ✅ Whether the account password, app password, or sign-in method is failing.
- ✅ Whether the mail profile, data file, or Outlook installation is damaged.
- ✅ Whether messages can send successfully after the blockage is cleared.
Need Help With an Email Stuck in the Outbox?
If your email is stuck in the Outbox and will not send, PcRiot can help identify whether the problem is the message, Outlook, the account, the device, or the mail server.
I help home users and small businesses in Perth with Outlook and email sending problems, including stuck Outbox messages, large attachment issues, authentication problems, and mail apps that will not send properly.