> "Email open" tracking just got a lot more reliable for all mass email & marketing automation vendors.
Has it? If Google's proxy is caching images, then "email open" tracking might have broken entirely. All the sender would see is that their email has been opened once by the proxy -- for all gmail addresses put together.
I'd imagine that they are going to de-dup the images they proxy which means email marketers need to generate unique images per mail and that means no more 1-pixel tracking images.
A solution would be 1-pixel high tracking lines - a 1 x 128 pixel wide image that encoded 0 and 1 as two RGB colors adjacent to the mail's background color in the visual spectrum so the difference isn't noticeable would encode a sha-1 hash placed in the url.
Mass-email senders probably would put a unique identifier in the image url (different for all users), so Google will open each image, because it can't know before loading them that it's the same image.
Has it? If Google's proxy is caching images, then "email open" tracking might have broken entirely. All the sender would see is that their email has been opened once by the proxy -- for all gmail addresses put together.