How to Fix the "External Recipients Not Allowed" Error in Gmail Mail Merge

If you or your team frequently use Google Workspace's built-in mail merge paired with Google Sheets, you might occasionally run into a frustrating roadblock: the "External Recipients not allowed" error.

This happens because Google Workspace defaults to strict internal-only sharing rules to prevent data leaks. Fortunately, if you have Administrator privileges, you can fix this across your domain in under a minute.

The 3-Step Admin Fix

1. Navigate to User Settings: Log into your Google Admin Console and go to Apps > Google Workspace > Gmail > User settings.
2. Enable External Settings: Scroll down the page until you locate the Mail merge block.
3. Apply and Save: Check both the "Allow mail merge" box and the nested "Allow for external recipients" checkbox. Click Save at the bottom of your screen.

SYSTEM NOTE: Security policy updates inside Google Admin can take anywhere from a few minutes up to 24 hours to fully propagate globally across your organization's user accounts.