The behaviour might change in the future, but I think an article in the Gmail help centre has some answers on the initial implementation of this: https://suppo

The behaviour might change in the future, but I think an article in the Gmail help centre has some answers on the initial implementation of this: https://support.google.com/mail/answer/145919?hl=en https://support.google.com/mail/answer/145919?hl=en "In some cases, senders may be able to know whether an individual has opened a message with unique image links" suggests Google (at least for now) fetches the images upon opening of the email.