In More > Setting > Receipt, you could set
1. Receipt number pattern
2. Receipt Template
You could upload the logo, header and footer to be displayed on the receipt. Clicking on Preview will show you how it look like before Save.
3. Receipt Email Template
You could input the content in the Text box. Click Show More to input placeholders in your emails.
4. Select Contact Method below and save.
Enabled Auto Send, receipt will be sent to the customer for every payment.