When you click "publish" thousands of copies are generated and sent to individual inboxes. Once you've sent an email, people can keep a copy of it in their archive, forever. You can't take it back.
I used to invest heavily in marketing automation, tracking, attribution, configuring funnels, and retargeting. But after 13 years of doing marketing for SaaS companies. But now I'm convinced that 90% of it is unnecessary.