[mikepurvis]

I don't think that's really the case, is it? At least, not in any formally-specified way. Modern email clients will extract metadata for things like airline reservations, shipping trackers, ICS calendar invites, etc, and give you live tiles specific to that time-sensitive info, but it's very clearly supplementary and at least in GMail none of it is pretending to be part of the message itself.

[IanCal]

Images are the clear thing that is typically remote - sometimes to the point of an email that’s entirely just an image, or rather a link to an image.

[mikepurvis]

Doesn't GMail pre-fetch those images and then cache them for the duration of the email being in your inbox, so as to defeat tracker dots, read receipts, etc?

[TheNewsIsHere]

You can, at the very least, register an open by generating unique URIs for any remote content.

I’m not sure how long Google caches it. I know Fastmail is doing the same thing now for any remote content fetched from within their web interface.

[ian-g]

Narvar's tracking emails are mostly-image

And on the one hand, it's cool as hell to see your email update itself to show tracking progress

On the other hand, just send me a new email. It's fine, I promise.

[TheNewsIsHere]

And if I’m ordering something of consequence, you’re damn right I want the time stamped paper trail of its movement you avowed.