I don’t not have mail chimp or constant contact enabled and my customer still receive emails when their items are shipped. Where are those settings? How do I change the message?
I am guessing that you mean that when you are processing an order in your POS system your customers are receiving email that their items will begin processing. This forum article should help you to understand how email templates are working and how to change the text within them: Using and Customizing NSc Mail E-Mail Templates
Please let me know if you need my further assistance on this.