E-Mail Marketing (Electronic Mail) is the means of sending messages electronically from one computer user to one or more recipients via a network. This form of marketing is extremely cost effective and a great way to keep past customers or potential customers interested in your business, by sending them promotional advertising with their permission. Key word: Permission. The customer list can be created by in store purchases at the POS or through a newsletter on your website. By gaining this permission to send notifications to a personal email you will not be considered spam.