The way I see this happening is to keep communicating with customers with a mailing list. One list for prospects, and one for customers. This is still marketing

The way I see this happening is to keep communicating with customers with a mailing list. One list for prospects, and one for customers. This is still marketing effort, but seems to be one way to go. Another, I guess, is to keep selling to customers as they are using your app/service online.