How to fix Mac Mail app emails stuck in Outbox and failing to send on macOS

Summary

This guide helps you troubleshoot and resolve: How to fix Mac Mail app emails stuck in Outbox and failing to send on macOS. Follow the steps below to fix the issue.

Common Causes

Emails stuck in the Outbox of the Apple Mail app on macOS usually indicate a connection problem with your outgoing mail server, a corrupted message, or an incorrect account setting. This guide walks you through the steps to clear the queue and restore sending functionality.

Quick Fix Steps

1. Check your internet connection by opening a website in Safari.
2. Open the Mail app and go to the Outbox folder.
3. Select any stuck emails and delete them or move them to Drafts to attempt resending later.
4. Restart the Mail app.
5. Try sending a new test email.

Detailed Instructions

1. Verify your internet connection

Ensure your Mac is connected to a stable network. If you are using Wi-Fi, try switching to a wired connection or a mobile hotspot to rule out local network issues.

2. Check the Outbox for large attachments

Emails with very large attachments often fail to send and block other messages in the queue.

1. In the Mail app, select the Outbox from the sidebar.
2. Identify any messages with large files attached.
3. Select the message and press Delete or drag it to the Drafts folder.
4. Remove the large attachment, reduce the file size, or use a file-sharing service instead.

3. Rebuild the Mailbox

Rebuilding the mailbox can resolve index errors that prevent emails from sending.

1. Open Mail.
2. In the menu bar, click Mailbox > Rebuild.
3. Select the affected account or mailbox.
4. Wait for the process to complete and try sending again.

4. Verify Outgoing Mail Server (SMTP) settings

Incorrect SMTP settings are a common cause of sending failures.

1. Open Mail and go to Mail > Settings (or Preferences on older macOS versions).
2. Click the Accounts tab.
3. Select your email account from the left sidebar.
4. Click Server Settings.
5. Ensure the Outgoing Mail Server (SMTP) details are correct.
6. If you are a 220 Internet Services customer, ensure you are using the SMTP settings provided in your welcome email.
7. Click OK to save changes.

5. Check for offline mode

Ensure Mail is not set to work offline.

1. In the Mail app menu bar, click Mailbox.
2. Ensure Take All Accounts Offline is not selected. If it is, click it to disable offline mode.

Troubleshooting

Emails still won't send

• Check your password: If you recently changed your email password, Mail may be failing to authenticate with the server. Go to Mail > Settings > Accounts and re-enter your password.
• Firewall or Security Software: Third-party security software can block outgoing mail ports. Temporarily disable the software to test if sending resumes.
• Port blocking: Some ISPs block port 25. Ensure your SMTP server is configured to use port 587 with TLS/SSL encryption.

If you have followed these steps and your emails remain stuck in the Outbox, please Open a Ticket for further assistance from our Brisbane support team.

Still Having Issues?