Scenario

Transaction email can be sent to customers through Invoice records only.

Solution

1. Update Customer Record

- Navigate to Lists > Relationships > Customers

- Edit any customer
- In the Preferences tab, uncheck Email next to Send Transactions Via
- Click Save

2. Update Custom Form
- Navigate to Customization > Forms > Transaction Forms
- Edit your preferred Invoice Form
- Go to Screen Fields tab> Communication:Messages tab
- In the To be E-mailed, mark the Default checkbox
- Click Save