Customers who opt-in to email marketing from your WordPress e-commerce website during checkout are added to a specified list on Constant Contact.
Visit constantcontact.com to register for an account.
Shopp is an ecommerce plugin for WordPress. Learn more about Shopp.
Yes, there are different extensions available including emailing marketing, short message service (sms) notifications, forms & reporting, help desk, and more. Please visit Shopp 101.