On: A Clever Way to Tell Which of Your Emails Are Being Tracked

Google actually uses an image proxy to thwart tracking based on images.[1]

http://googlesystem.blogspot.ca/2013/12/google-uses-proxy-to...

Which won't work if it's a unique image (since it won't be in the proxy). And if it is a tracking image, it'll probably be unique.

If it's a unique image, then presumably Google reads it and pre-caches the image on receipt. So all you'll get from 1 pixel image is confirmation of email delivery, which is something you get with SMTP anyway.

Of course if Google wait to cache the image when you actually read it, then this isn't true. But I'm prepared to give them more credit than that.

> So all you'll get from 1 pixel image is confirmation of email delivery, which is something you get with SMTP anyway.

You'll get a read-receipt, which SMTP doesn't offer.

AFAIK they do this for all images. Not just commonly embedded images.

Except it doesn't thwart tracking the actual open. Just the IP of the end user, etc: http://techcrunch.com/2013/12/12/gmail-open-rates/