Despite the growing popularity of messaging services like Slack, email still reigns supreme as the business communications medium of choice: more than 205 billion emails were sent per day in 2015. It’s no surprise, then, that email is also a major workplace stressor, with 92% of employees showing elevated blood pressure and heart rate when using email at work. Even when they’re ignoring email, it often gnaws at their consciousness; leaders like Zappos CEO Tony Hsieh have spoken about their guilt and anxiety from failing to clear out their inbox and respond to messages in a timely fashion.