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Outlook email stuck in Outbox: what it means and how to fix it

Short answer

An email stuck in the Outbox means Outlook accepted your message but could not hand it to the mail server. Usually Outlook is offline, the attachment is too big for the server, or your password changed. First make sure Outlook is not set to Work Offline (Send / Receive tab), then press F9 or click Send/Receive All Folders to retry.

What this message means

The Outbox is a holding folder. When you click Send, Outlook puts the message there and tries to pass it to your outgoing mail server. If that handoff fails, the message waits in the Outbox, often shown in italics, and Outlook keeps retrying in the background. Nothing has reached the recipient yet. The cause is almost always on your side: no connection, Outlook set to offline, an attachment larger than the server allows, wrong or expired sign-in details, or a setting or rule that delays sending. Occasionally a security program or a damaged folder structure blocks it. One oversized message can also hold up every message queued behind it.

Common causes

CauseHow to tell
Outlook is set to Work Offline or has lost its connectionThe status bar at the bottom of classic Outlook says "Working Offline" or "Disconnected", and the Work Offline button on the Send / Receive tab looks pressed in. New emails also stop arriving.
The message or attachment is larger than your mail server allowsOnly messages with big attachments get stuck, while short text-only emails send fine. The status bar may show a send progress bar that never finishes, and other messages pile up behind the large one.
Your password changed or the account settings are wrongOutlook repeatedly asks for your password, shows a Send/Receive error mentioning authentication or the outgoing (SMTP) server, or the problem started right after a password change.
"Send immediately when connected" is turned off, or a rule or Delay Delivery is holding the messageMessages sit in the Outbox until you press F9 or click Send/Receive, then go out fine. Or every message waits a fixed number of minutes before sending, which points to a "defer delivery by # minutes" rule.
You opened the message while it was waiting in the OutboxThe message was in italics, you opened or clicked it, and now it is no longer in italics and stays put even though other emails send normally.
Antivirus email scanning, a faulty add-in, or a damaged mail folderEverything looks correct but sending still fails, it works in Outlook on the web, or on a Mac you see "Unexpected data was encountered" and the Sent Items folder is missing or shows the wrong icon.

How to fix it

1. Turn off Work Offline and retry the send

  1. Classic Outlook for Windows: open the Send / Receive tab. If Work Offline is highlighted, click it once to go back online.
  2. New Outlook for Windows: go to Settings > General > Offline, turn off offline email, calendar and people, then close and reopen Outlook.
  3. Outlook for Mac: open the Outlook menu at the top of the screen and make sure Work Offline is not checked.
  4. Confirm you have internet access by opening a website. If not, restart your router and wait for the connection to return.
  5. Press F9 (Windows) or click Send/Receive All Folders to force Outlook to try again.

2. Remove or shrink a large attachment

  1. Switch Outlook to Work Offline first so it stops trying to send the stuck message (Send / Receive tab > Work Offline).
  2. Open the Outbox and drag the stuck message to the Drafts folder. If you just want to cancel it, right-click it and choose Delete.
  3. Open the message from Drafts, click the attachment and press Delete.
  4. Upload the file to OneDrive, Google Drive or Dropbox and paste a share link into the message instead. Most servers reject messages over about 20 to 25 MB, and attachments grow roughly a third in size when sent.
  5. Turn Work Offline back off and click Send.

3. Resend a message you opened while it was in the Outbox

  1. Drag the stuck message from the Outbox to the Drafts folder.
  2. Open it from Drafts.
  3. Click Send. It should return to the Outbox in italics and send within a few seconds.
  4. While messages are sending, avoid clicking on them in the Outbox.

4. Turn on "Send immediately when connected" and check delay rules

Classic Outlook for Windows (Outlook 2010 and later, including Microsoft 365)

  1. Go to File > Options > Advanced.
  2. In the Send and receive section, tick Send immediately when connected and click OK. If it is greyed out, your organisation controls it through Group Policy, so ask IT.
  3. Go to Home > Rules > Manage Rules & Alerts.
  4. Click each rule on the Email Rules tab and read the Rule description. Any rule that says "defer delivery by # minutes" delays sending. Double-click it and clear that action, or delete the rule.
  5. Open the stuck message, go to the Options tab and make sure Delay Delivery is not turned on.

5. Update your password and outgoing server settings

Classic Outlook for Windows. On Mac use Outlook > Settings > Accounts; in new Outlook use Settings > Accounts.

  1. Sign in to your email in a web browser (for example outlook.com or your provider's webmail) to confirm your password works.
  2. In Outlook go to File > Info > Account Settings > Account Settings, select the account and click Change (or Repair).
  3. Enter the current password and finish the wizard.
  4. For IMAP or POP accounts, check the outgoing server details from your provider. Common values are port 587 with STARTTLS or port 465 with SSL/TLS, with outgoing server authentication turned on.
  5. Restart Outlook and press F9.

6. Clear a message that will not move or delete

Classic Outlook for Windows

  1. If Outlook says it has already begun transmitting the message, close Outlook.
  2. Press Ctrl+Shift+Esc to open Task Manager, select any remaining Microsoft Outlook process and click End task.
  3. Press Windows key + R, type outlook.exe /safe and press Enter. Safe mode starts Outlook without add-ins.
  4. Set Work Offline, then delete the message or drag it to Drafts.
  5. If sending works in safe mode, disable add-ins one at a time under File > Options > Add-ins > Manage COM Add-ins > Go to find the culprit. Also try pausing your antivirus's email scanning.

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Still not fixed?

Send the email from your provider's webmail (Outlook on the web, Gmail, etc.). If it sends there, the problem is inside Outlook on your computer, so run an Office repair (Windows: Settings > Apps > Installed apps > Microsoft 365 or Outlook > Modify > Quick Repair, then Online Repair) or remove and re-add the account. If it fails in webmail too, the problem is your account or mail server, so contact your email provider or IT department and give them the exact error text. On Mac, if you see "Unexpected data was encountered", ask your admin to reset the mailbox's default folders.

Questions people ask

How do I delete an email stuck in the Outlook Outbox?

Turn on Work Offline from the Send / Receive tab, then right-click the message in the Outbox and choose Delete. If Outlook says it is already sending the message, close Outlook, end it in Task Manager, reopen it offline and delete the message.

Why do my emails only send when I press F9 or Send/Receive?

The "Send immediately when connected" option is turned off. Turn it back on under File > Options > Advanced > Send and receive.

Why is my email in the Outbox shown in italics?

Italics mean Outlook has the message queued and is trying to send it. If it stays in italics for more than a few minutes, Outlook cannot reach the server or the message is too large.

Will the recipient get an email that is stuck in my Outbox?

No. A message in the Outbox has not left your computer. It is only delivered once it moves to Sent Items.

What is the attachment size limit in Outlook?

It depends on the mail server, not Outlook itself. Outlook.com and many providers cap attachments at about 20 to 25 MB, and Microsoft 365 business accounts allow larger messages depending on admin settings. Use a cloud share link for bigger files.

Sources

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