This is particularly annoying, because if they just cached the image immediately upon receiving the e-mail, there would be no privacy impact AND you would get t

This is particularly annoying, because if they just cached the image immediately upon receiving the e-mail, there would be no privacy impact AND you would get to see the image. (Yes, it might still send your e-mail address to third parties, but someone who has your e-mail address is free to send it to anyone they want without your help; there is no way to stop that.) I guess we didn't need further evidence that Google cares more about third party marketers than users' privacy.