A pre-emptive opt-out could work, but how exactly would you implement it?

Do I have to give you all my email addresses that I want to opt-out with?

Do I have to get an "optout" cookie so that the server with the tracking pixels and whatnot knows not to track me?

I think I'd rather block this at the email client level. This way I don't have to trust anyone's optout procedures, as well as being protected from any nefarious trackers that don't care about things such as opting-out.