Foiling Electronic Snoops in Email

By some estimates, trackers are now used in as much as 60 percent of all sent emails.
The trackers are traditionally offered by email marketing services like GetResponse and MailChimp.
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I began by testing the email trackers themselves. One was MailTrack, which is a plug-in for Google’s Chrome browser that can quickly insert a hidden tracking pixel into a message. Setting it up is simple. You install the plug-in and enable a Google mail account to use the service. After typing an email, you hit a double check mark icon to embed the invisible tracker. When the recipient opens the email, you receive a notification and an email alerting you that the message has been opened.

 http://www.nytimes.com/2015/11/19/technology/personaltech/foiling-electronic-snoops-in-email.html?ref=technology