Brands that embrace responsive design see 24% more clicks than brands that don’t, according to Yesmail’s Q4 2015 email marketing compass. The report’s final verdict: Mobile is indispensible for continued growth and better performance from email campaigns.Email will reach 3 billion users by 2020, according to the Radicati group, growing 3% YoY for the next three years. Currently, over half of all email opens happen on mobile devices. That number will likely increase as users spend more time on and become more invested in their devices.About 55% of brands use responsive design all the time or most of the time in their email campaigns, according to Yesmail’s report. Those brands that don’t pay attention to or implement a mobile strategy as simple as responsive design are missing out on relatively easy engagement with their customers.Despite the fact that more consumers are receiving more emails than ever, the number of click and opens per opener continue to rise. This may be due to improving mobile designs and savvier marketers employing strategies that don’t push mobile users away from the get-go.