What are email providers supposed to be solving here? The reality is as an individual it's up to you how your mail client behaves and what emails you decide open or not... The hidden reality of the email situation for on the sender side is that it's getting increasingly hard to even send mail as an avg entity instead of outsourcing the problem to google/aws/mailchimp/whoever and that's not an accident.
As for your mail: almost every marketing/transactional/non-personal you've had over the last few years will have 'completely unique to you and that /specific/ message' urls for things like the images (if they're not inlined), tracking pixels, and especially the links you can follow from the mail which allows the marketers/esp's to see who has opened it, who clicked, who didn't and so on. If there's html/js allowed then we'll be watching which parts your mouse hovers over, how fast you scrolled, which parts you actually read and so on. Do a tcpdump while you read some mails from amazon or someone and see what you find when you move your mouse around.
Hopefully that isn't news to anyone. This has been happening for ages. If a non-transactional mail is going to 100k people then for example the banner image at the top will have 100k urls the webserver will serve it which is how you track that stuff without cookies..
To explain further, mails more often than not today are viewed in a browser (even the 'fat' mail apps like mail.app or I presume outlook use 'embedded browsers/web views' which are the same) these all happily send the cookies you've got kicking around from your normal sessions for those domains on the images, which, are then matched up with whatever else you'll do on said site (or even better, if the tracking is coming from a diff domain and multiple sites use the same provider then we'll be tracking you across a lot of dofferent places (see: omniture, google, etc) -- generally a MSP/tracking provider can't give a client access to what a user in a given segment might be upto on sites that they don't own, but the SP certainly knows and the biggest one also controls a lot of the ads...).
What's one email ring?
edit: Email providers do have some protections too, though. SPF has been around for ages which if you're not the MX ip and don't have the record for the domain you're FROM'ing gets you on bumped up the process of making the shitlist on the big MX's at least (gmail, hotmail, whoever). Finally getting listed means they won't accept mails from that IP for 24 hours (I assume it's 24 hours simply because it'd be insane to sustain an actual blacklist longer than that on the scale things are today, and that stops people having to request removal after hacks or whatever..
Things are getting better with DKIM and DMARC too...