The guiding principles behind Do Not Track aren’t just for web browsers and pages. Tracking happens in a variety of ways, including through email, so we’re putting Do Not Track into Thunderbird.
Email Tracking. Sometimes email messages you receive contain external images — images that need to be loaded from the web to display the entire content of the message. This includes pixel tags and clear gifs. When your mail client renders the message, it has to go fetch the images from the web using the same technologies as a web browser. The upshot is that when the email is drawn on your screen, a web server can learn that you opened the message; this is how email tracking works. By attaching a unique ID to the URL for the image, the server can also know which specific message caused the request — including to which email address the message was sent. Email marketing organizations often use this information to track which messages you read, which links in messages you click, and then provide more customized messages in the future.
Thunderbird Support. A little while ago, I landed a patch that will add Do Not Track support to Thunderbird 15. While that release is a number of weeks away, if you’re using the Daily builds of Thunderbird, you’ve got the feature in Security options. This means that when you open email messages sent by marketing firms, you can enable DNT in Thunderbird to let them you don’t want to be tracked.
Next: Building Do Not Track into Thunderbird is just the first step. Next we will work with email marketing software providers to honor the DNT request. We’re reaching out to email industry leaders and introducing them to DNT and will keep you updated on what happens.