I have an eCommerce site and sell physical products. I currently have a customer list of about 2,500. A small percentage have opted to receive emails, but I have not done any email marketing. I would like to start sending out periodic specials and coupons, but I would like to first contact the entire database to see if I can get more to opt in. I don't want to get in trouble for sending emails to my customers that haven't opted in. Any advice?