[SamBam]

Your method seems to just involve knowing the standard rules that mail services use to provided tracking information, and removing those or reverse engineering them.

What happens when one of the biggest email services, Apple, starts removing those tracking IDs? Marketing just rolls over and dies?

It will be pretty trivial to keep changing up their url parameter system, or even to have unique urls that don't include query parameters at all, like the MailChimp system but without the simple Base64 encoding. Sure, it would be a bit of a pain to engineer, but needs must.

It seems this would be better to make a browser extension, which can keep up with changes, and, honestly, would probably be small enough that marketers wouldn't bother trying to adapt to it.