Hi,
Email clients in general don't support video in emails.
If you see a video in a newsletter, that is NOT the real video but faked one.
The following link can give you an idea of how to achieve it.
You can see how this guy did it for another newsletter platform but the principle is the same
https://www.youtube.com/watch?v=gRLYG9o6Y6M.
Basically, you create an animated GIF out of the video content and use that animated GIF in the newsletter.