Hi @Katerina1 , most brands that want to embed video in a newsletter pay services like Movable Ink or Live Clicker, as they have code that allows this to work for various email clients or default images to be seen in other clients.
As Manoj mentioned, while it is possible but it is not recommended to embed a video in the email/ newsletter as it will also increase the email size and impact the deliverability. Rather you can host the video on a web page and provide the link in the newsletter. This would also improve the throughput and simpler to implement.
Please also refer to the below post for video recommendations: