A service product works for coaching or consulting products or services where you do not want your user to have login details to your CCK website.
User login or new user registrations will not be created in your CCK membership area for service products.
When your customer buys a service product, they receive one single automated system email from CCK as shown below.
System Email: Email Invoice
When a member buys a product through a checkout page (automatic), the system sends an automated invoice email with a summary of the products they purchased.
Email Subject: Your order is complete
Sender Email: the email address you added under Applications> Email Server