Send & Receive Issues

Fix Word Mail Merge Emails Stuck in Outlook Outbox on Mac

WPS Content Manager Oct 12, 2026 869 views

Question details

User is unable to send mail merge emails from Word via Outlook on a Mac, as they remain pending and stuck in the Outbox.

How to Fix Word Mail Merge Emails Stuck in Outlook Outbox on Mac

Product: Microsoft Word and Outlook
Device & OS: macOS
Scenario: Performing a mail merge in Word to send mass emails through Outlook.
Observed behavior: Mail merge emails stay pending in the Outlook Outbox and do not send, even after restarting or reinstalling Word.

Before you start

Ensure your Mac is connected to a stable internet network and that your email account password hasn't recently expired.

Solution 1Recommended

Verify Outlook Connection and Default Mail Settings

Ensure Outlook is correctly configured as the default mail client and is actively connected to the server.

Often, mail merge emails get stuck because macOS does not recognize Outlook as the primary mail application, or Outlook has quietly lost its connection to the Exchange or IMAP server.

Set Default Email Reader

Open the built-in Apple Mail app. Go to 'Mail' > 'Preferences' (or Settings) in the menu bar, and change the 'Default email reader' to Microsoft Outlook.

Check Outlook Connection

Open Microsoft Outlook. Look at the bottom right corner of the application window to confirm it displays a 'Connected' status without any warning icons.

Send a Test Email

Draft a standard, new email directly within Outlook and send it to yourself. If this email also gets stuck, you need to resolve your basic Outlook connection issues first.

Verify Outlook Connection and Default Mail Settings

Pro Tip: Keeping Outlook open and actively running in the background before initiating the mail merge in Word often prevents the Outbox queue from freezing.

Solution 2

Update Office Applications and Re-authenticate

Outdated software or authentication glitches can block communication between Word and Outlook.

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Try WPS Office for Reliable Document Creation on Mac

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1. Download WPS Office: Visit the official WPS Office website and download the macOS version.
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Frequently Asked Questions

Why are my Outlook emails stuck in the Outbox on my Mac?

Emails can get stuck if Outlook is set to 'Work Offline', if there is a problem with the outgoing mail server (SMTP) authentication, or if large attachments exceed your provider's sending limits.

Does reinstalling Microsoft Word fix mail merge issues?

Generally, no. Reinstalling Word rarely resolves Outbox synchronization issues because the problem usually lies in Outlook's account configuration, connection status, or macOS system preferences.

How do I ensure Word can communicate with Outlook during a mail merge?

Make sure Microsoft Outlook is set as the default mail application in your Mac's system settings (or Apple Mail preferences). Additionally, always launch Outlook and ensure it is fully connected to the mail server before you click 'Finish & Merge' in Word.

Outlook & Email Problems