How do I edit the donation receipt template for one-time and subsequent recurring donations?

You can edit your one-time and first-time recurring email receipt by going to the Receipt Email tab of your campaign editor. 

This section will provide an editor to amend this template. 

Donorbox also sends donation receipts after charging your recurring donors each month. You can customize the content of these email receipts by clicking Engage and then Receipts link on the left.