There is still a way to track opens for images but it is now impossible to detect device and location.

That has got to be a neat trick. If a Google server does the fetch, how would you detect opens other than theirs?

Uniquely name at least one image per outgoing email where the image name is tied to a recipient ie a316f002a5d080a613dce89a4ad8f9a9.gif uniquely identifies [email protected]. If google doesn't fetch the image until you open the email you can also determine open time. If they request and cache all images at the time the email is received regardless of its having been opened then this doesn't work.

Thanks, the next question is if gmail sees a bunch of emails from the same sender with these hash-named images, I wonder whether they will squash them.

How this plays out will be interesting to watch.

They are already scanning the content of the emails so there's nothing stopping them from determining if the images between emails are the same regardless of name, and even then just sending down whatever they have cached, 1px transparent gifs are still common for this. Could break some a/b testing software though. You could see marketers move to including a unique image per recipient like a gravatar. If it were me I'd just include something like the github avatars in the footer of every message. Google can learn that those are tracking images and block them but will they?

"Thanks, the next question is if gmail sees a bunch of emails from the same sender with these hash-named images, I wonder whether they will squash them."

Are you saying squash the sender or squash the tracking images?

I hope gmail doesn't start squashing my emails because it contains a tracking pixel.

Easy: a unique image URL for each recipient. Seems like a huge win for marketers and spammers.