Haven't read the whole article yet, but I'm aware of these trackers, that's why I never lie about when I opened some mail LOL. But I wasn't aware of anti-tracking services, perhaps this could be implemented in ad-blocking extensions? Or even better, it should be implemented in email clients both desktop and web-based.
I thought common email clients already block any download of external data by default (e.g. Outlook 2016) unless the email of the sender is the trusted list. Possibly this is only relevant to web based email clients?
Yes, Thunderbird behaves the same. And there is a second line of defense: I'm using uBlock Origin in Thunderbird and I block everything in the global column of uB0's Dynamic Filtering by default. If I allow external data in order to have an email of a specific sender properly displayed I create a noop rule in the local column only for those cells which are absolutely necessary. This means that all 3rd party stuff (trackers) remains usually still blocked. And if in few cases 3rd party stuff has to be allowed the built-in filterlists do their bit. So no - I'm not worried about email tracking at all.
