There is no upper cap on the size of the attachment, but sending huge files as an attachment is a not a good practice.
Do not attach the video itself to the delivery as the email may become very heavy weighted and could be rejected or blocked either by ESPs or recipients.
Large sized emails, which would be the result of embedding a video, would greatly reduce the deliverability. Additionally, emails with videos embedded in them are generally handled by all ISPs as SPAM due to the infrequency of their occurrence in regular email communication.
You can to though below similar thread
https://forums.adobe.com/thread/2277514
