Interactive emails embed live functionality inside the message (AMP for Email or kinetic CSS): carousels, accordions, polls, add-to-cart, or appointment booking that work without leaving the inbox. The best ones remove a step from a real task, like confirming an RSVP or browsing products, rather than adding novelty. Build a static fallback first, since client support is uneven, and reserve motion for the one moment that earns the tap.