This is a weird thing to write about in 2025. AMP emails didn't really take off / get any kind of adoption did they. And HTML emails, annoying and problematic as they are have come a long way from the mess of client support and complete hack-job coding to where they are now thanks to standards and largely the popularity of web-based clients and the benefits those bring for email reading. GIFs inside emails unthinkable and ridiculous ten years ago. Today, not a big deal really for a good chuck of audiences. Etc.