We spend an enormous amount of time managing our inboxes – 28% of our time each week, actually. That's according to a report from the McKinsey Global Institute. They estimate that 13 hours of our time each week is spent reading, organizing, and responding to emails. And that's just for work.

Email costs us more than time, too. According to Tom Pisello, aka The ROI Guy, email overload costs organizations about $5,000 per user in lost productivity each year.