Thanks for doing this. Love seeing privacy coming up front and center. FYI- if you're using web-based email (e.g. Gmail), a browser extension like PixelBlock will zap most shady trackers. I would love it if there was a Hey-like mobile client for Gmail (and other email providers). It's still hard to block this tracking on mobile.
If you're on Android, FairEmail is worth a look, as a mail client that thinks about privacy. There's blocking of images by default, as well as an option to safely render basic HTML without having to parse full HTML email (if you don't like that). Also has some detection of common tracking parameters or redirect services for hyperlinks, and lets you remove these automatically before visiting a link. Not as shiny as Hey for sure, and a more technically focused email app, but if you want something privacy oriented, it's good and supports IMAP/SMTP nicely. Open source too, which is always nice.
Not affiliated, just a happy user for a few years.
I just go for the bazooka approach and block every single image in my Gmail and only load them on a case-by-case basis. I've been paranoid about email tracking ever since I first saw my father insert a read-receipt via Outlook into a work email sometime in the late 90s or early aughts.
