Go to your dashboard and press the plus (+) button to create a new mail tracking. A new page will appear, enter a name for your new mail tracking and press the create button. You will then see a dialog below 'Trackable pixel'. You can either copy the image itself and paste it in your outgoing email or copy the HTML-code in case you are creating a HTML-mail. Be careful not to add it more than once, otherwise your tracked data will contain double the data. Notice that the trackable pixel is invisible. You can then send your email to the recipients. Go to your dashboard and press the mail tracking with the name that you created. Whenever there is some data tracked you will see it over there.