Sorry, I wasn't precise. I was responding to the suggestion to only proxy for familiar senders. But, assuming that you can correctly identify who is familiar and who's not (there is scam detection as well), the benefit is minimal.
There is bigger benefit of doing this proxy for non-familiar emails.
Google could prevent leaking if email address is valid by simply prefetching images even when email is sent on non existent accounts.
There is bigger benefit of doing this proxy for non-familiar emails.
Google could prevent leaking if email address is valid by simply prefetching images even when email is sent on non existent accounts.