A Clever Way to Tell Which of Your Emails Are Being Tracked

While you've likely never heard of companies like Yeswear, Bananatag, and Streak, they almost certainly know a good deal about you. Specifically, they know when you’ve opened an email sent by one of their clients, where you are, what sort of device you’re on, and whether you’ve clicked a link, all without your awareness or consent.

http://www.wired.com