And that's true even if the client, like gmail, proxies the images: https://gmail.googleblog.com/2013/12/images-now-showing.html https://gmail.googleblog.com/20

And that's true even if the client, like gmail, proxies the images: https://gmail.googleblog.com/2013/12/images-now-showing.html https://gmail.googleblog.com/2013/12/images-now-showing.html