What do you mean it's personalized? It's an anonymous identifier token specific only to that email.
Like I said, even with HTTPS everyone in the cafeteria theoretically knows you're connecting to HBSC as well.
So I don't see the difference.
They know that you likely read some email from HSBC and if you happen to read the same one again they will know it was the same one.
What on earth makes you think it's anonymous?
It's trivial to encode each tracking pixel with a personalized hash of some sort linking it to the intended recipient of that particular email.
This is...just how tracking pixels work.
You _think_ it's anonymous.