Hey! Thanks for posting this.
Author here.
This investigation into email tracking attempts to deconstruct tracking links and pixels and highlight the data that is being collected. It covers Mailchimp, ConvertKit, Substack and other Mailgun retailers.
There's also some attempted (albeit unsuccessful) reverse-engineering of an opaque token in the Substack section (If you like reading stuff about reverse-engineering).
Happy to answer any questions.
Thanks.
