Hi Lauren Hassett, welcome to the job board. Sounds like your trying to solve some underlying problem that you think video will somehow fix while not being explicit with the consequences, like maintenance and cross-client issues. I can provide guidance on this or discovery to identify solutions to root problems. Contact me with details for rates email@example.com.
Email is not where video belongs, yes at some point it may become a trend but just like blinking red text, or autoplaying sound on websites you should never do it as it takes a type of control AWAY from the user and will become an anti-practice and mark of spammers.
The exception here is video as an attachment but only if your business model is selling video.
Just look at youtube there entire model is video but they don't embed video, why should you?
Technically you can but there is no point currently as email app support is spotty and not to be relied on. https://www.campaignmonitor.com/dev-resources/will-it-work/video/
Instead an IMAGE(screenshot) of the video-player could be put in the email and link it to the external video. So users can choose to interact with a video instead of forcing thier client to load a video player.
Alternatively use a gif, but only do this if you understand how to do this properly since a batch of annoyed customer that have given you money is risk.