Brian Merchant

As recently as the mid-2000s, email tracking was almost entirely unknown to the mainstream public. Then in 2006, an early tracking service called ReadNotify made waves when a lawsuit revealed that HP had used the product to trace the origins of a scandalous email that had leaked to the press. The intrusiveness (and simplicity) of the tactic came as something of a shock, even though newsletter services, salespeople, and marketers had long used email tracking to gather data.