How to Fix Outlook Emails Stuck in Outbox and Not Sending

Summary

This guide helps you troubleshoot and resolve: How to Fix Outlook Emails Stuck in Outbox and Not Sending. Follow the steps below to fix the issue.

Common Causes

When Outlook refuses to send emails, the culprit is usually a stuck message in the Outbox, a working offline mode, a misbehaving add-in, or a corrupted profile. This guide walks you through the most common causes and the steps to resolve them, starting with the quickest fixes before moving to deeper troubleshooting.

Quick Fix Steps

If you only have a minute, try these in order. Most send issues clear up after the first two.

1. Check your internet connection by opening a browser and loading any website.
2. Confirm Outlook is not in Work Offline mode. Look at the bottom status bar; if it shows Working Offline, click Send / Receive > Work Offline to toggle it off.
3. Open the Outbox folder. If a message is stuck, open it and click Send again, or drag it back to Inbox, edit, then resend.
4. Restart Outlook completely (close from the system tray on Windows, or Cmd + Q on Mac).
5. Reboot your computer if the issue persists.

Detailed Instructions

1. Clear Stuck Messages from the Outbox

A message larger than your server limit, or one with an invalid recipient, will often sit in the Outbox and block everything behind it.

1. Switch to the Outbox folder in the folder pane.
2. Click the stuck message to open it in the reading pane or a new window.
3. Check the To, Cc, and Bcc fields for typos or invalid addresses.
4. If the message is unusually large, reduce the attachment size or use a file-sharing link instead.
5. Press Send. If it stays stuck, move the message to Drafts by dragging it, then delete the original from Outbox.

2. Disable Work Offline Mode

Offline mode prevents Outlook from connecting to the mail server entirely.

1. Click the Send / Receive tab on the ribbon.
2. Look for the Work Offline button. If it is highlighted, click it once to go back online.
3. Confirm the status bar at the bottom of Outlook no longer reads Working Offline.

On Outlook for Mac, the toggle is under Outlook > Work Offline in the menu bar.

3. Check Account Settings and Passwords

An expired password or authentication issue can leave Outlook trying to send without success.

1. Go to File > Account Settings > Account Settings.
2. Select the affected account and click Repair (or Change on older versions).
3. Follow the prompts to retest the connection. If prompted, re-enter your password.
4. Click Next and allow Outlook to complete the configuration.

For step-by-step help configuring accounts from scratch, see Setting Up an Email Account in Outlook (POP/IMAP/Exchange).

4. Start Outlook in Safe Mode (Windows)

Safe Mode loads Outlook without add-ins, which is the fastest way to determine whether an add-in is the cause.

1. Close Outlook completely.
2. Press Win + R, type outlook.exe /safe, and press Enter.
3. Confirm by clicking OK in the dialog that appears.
4. Try sending a test email. If it sends successfully, an add-in is the cause.

To isolate the offending add-in:

1. With Outlook open normally, go to File > Options > Add-ins.
2. At the bottom, change Manage to COM Add-ins and click Go.
3. Uncheck the first add-in and click OK, then test sending.
4. Repeat until sending works, then re-enable the others.

5. Recreate the Outlook Profile

If the above steps have not resolved the issue, the Outlook profile itself may be corrupted. This is more involved, so back up your data first.

For instructions on backing up your mailbox data, see Backing Up and Restoring Outlook Data Files (.pst/.ost).

1. Open the Control Panel and search for Mail (Microsoft Outlook).
2. Click Show Profiles.
3. Click Add, name the new profile, and configure your email account.
4. Under Always use this profile, select the new profile and click OK.
5. Open Outlook and test sending.

6. Check Send/Receive Settings

Sometimes Outlook is configured to send only on a schedule, or the send/receive group has been disabled.

1. Go to Send / Receive > Send/Receive Groups > Define Send/Receive Groups.
2. Confirm Schedule an automatic send/receive every [X] minutes is enabled.
3. Click Edit and verify the Outbox folder is included in the group.
4. Click OK to save.

For broader guidance on send/receive errors, see Troubleshooting Outlook Send/Receive Errors.

Troubleshooting

Emails Send but Disappear

If messages appear to send but never arrive, check your Rules for one that moves or deletes sent items. See Organising Emails with Rules and Alerts in Outlook for details.

Mac-Specific Checks

1. Open System Settings > Internet Accounts and confirm the account is enabled.
2. In Outlook for Mac, choose Outlook > Settings > Accounts and re-enter the password if prompted.
3. Open Keychain Access (in Applications > Utilities) and remove any outdated Outlook or Microsoft credentials, then sign in again.

Antivirus and Firewall Interference

Some third-party security tools scan outgoing mail and can block or delay it. Temporarily disable the email-scanning feature (not the whole antivirus) and test sending again.

Large Attachments or Recipients

Microsoft 365 has a 25 MB message limit, and many servers cap attachments at 20 MB. If your message is too large, it will stay in the Outbox. Consider using a file-sharing link instead of attaching the file directly.

Still Seeing the Same Issue

If none of the steps above resolve the problem, the issue may be on the mail server side or with your Microsoft 365 licence. Gather the following before contacting support:

• The time and date of the last successful send.
• The exact error message shown in Outlook, if any.
• A list of troubleshooting steps you have already tried.
• Your Outlook version (File > Office Account > About Outlook).

With this information, your IT support team can investigate server-side delivery, mailbox quotas, or licensing issues more efficiently.

Still Having Issues?