I have a new Macbook Pro and use Mac Mail. I want to figure out how to completely disable image downloads as I discovered that certain people I email with use an app called Message Tag, which embeds a small image into the message allowing them to be notified when I open their email. I find this an invasion of privacy and want to be able to block this. I unchecked the box for "Display remote images in HTML messages" in the viewing section of my mail preferences, but I am not confident that this will solve the problem, as I don't know if their secret images are in HTML or not. Any advice on how to block people from using this?