Mail Merge Tab is Missing in the Custom Record

1. Navigate to Customization > Lists, Records, & Fields > Record Types.
2. Click any List to view the record.

Result:  No Mail Merge tab to click the Email button.

Solution:
1. Navigate to Customization > Lists, Records, & Fields > Record Types.
2. Click the Custom Record created.
2. Set the Enable Mail Merge check.
3. Click Save.
4. Go back to Customization > Lists, Records, & Fields > Record Types.
5. Click any List to view the record.

Actual Result: The Mail Merge tab is now available to send email.