Text message marketing (also referred to as SMS marketing, mobile marketing, or text message marketing) is an ecommerce marketing method that involves delivering promotional messages to customers via text message (SMS, or short message service). Before businesses can contact their audiences via text messaging, customers must opt-in or subscribe to give their permission to receive promotional SMS messages. On the business side, SMS marketing campaigns allow for increased customer engagement and conversion rates, and are a powerful tool for increasing customer retention, freeing up customer service resources, and increasing retention and MRR.