When referring readers to an external video in your email, what visual element can help increase the click-through rate?

A thumbnail graphic with a clear "play" button is most effective because it visually cues the recipient that there's video content available and encourages interaction. The "play" button is universally recognized, making the call to action intuitive. An animated GIF of the video might be too large in file size, slow to load, or not render correctly in all email clients, potentially frustrating the user. A large "Buy Now" button is irrelevant if the primary goal is to drive video views, and it misrepresents the content. A screenshot of the video title lacks the visual cue of a play button, making it less engaging and less clear that the image is clickable to watch a video.