Opt-out
Although it is possible to opt-out of email tracking, doing so does not come without sacrifice. Within one's individual email client, one can turn off image display, disable the display of links, and decline any read-receipt requests.
One should note that there are email tracking services which convert the email message into an image before delivering the message. One obviously cannot read the message contained in the image if image display is disabled in one's email client.
Read more about this topic: Email Tracking