How does the tracking-pixel mechanism work?

The tracking pixel is a `1x1` transparent GIF or PNG image hosted by your ESP. When the recipient’s email client loads images, it requests that pixel from the ESP’s server. That request contains metadata such as user agent, timestamp, and approximate location.

It is similar to a tiny lantern signal sent back across the sea. When it lights up, you know the message was seen through a porthole but not necessarily read.