This document discusses optimizing emails for mobile devices. It notes that up to 50% of email opens are now on mobile and mobile purchasing is most influenced by emails. It recommends that marketers monitor mobile open and engagement rates, review the customer journey, and define key performance indicators. The document then discusses responsive design for email, which allows content to resize and reflow for different screen sizes from a single email version. It provides examples and notes benefits like image resizing and removal of horizontal scrolling. Sources for further information are also included.