In order to start tracking your outgoing e-mails, you must have an e-mail program in which you can insert HTML (preferred) or an image such that the image uses the PastePixel pixel URL.
When you've composed your e-mail as you normally would do, you go to your pastepixel dashboard and create a new mail tracking. You give your mail tracking a name, this name will be used as reference on your dashboard. From this screen you can add custom data to your pixel or add trackable URLs. You can also do this later.
In the “Tracking pixel” panel you will see two input fields: Pixel URL and pixel HTML. The best method is to copy the pixel HTML-code and insert it in to your e-mail. It does not matter where you place it, as it will be invisible. Do make sure that you insert it as HTML and not as text. For example, if you use Thunderbird, you have to use the insert HTML option (Insert > HTML...). Alternatively, you use the URL of the pixel to insert the image. You can only do this if the image does not get copied to an offline version.
After sending your mail you can continue to your mail tracking page and analyze the data.