Hope this helps!
Not all users can receive html emails and text emails can't have embedded videos. Unfortunately, Marketo doesn't support file attachements in emails either. As Kenny suggested, you can put a link to a web page with a video in your emails.
Campaign Monitor has a good primer on this: http://www.campaignmonitor.com/resources/will-it-work/video/
Key takeaway: video is again becoming available to embed in emails with HTML5, but its probably not worth the investment for most companies.
That is a really great article that Steven posted. I would also reccomend perusing Campaign Monitor's Blog and Resources section for other very good information in regards to email marketing and the like.
We have got video succesfully working outside of Marketo into some mail clients. However as soon as we upload into Marketo the video effort is disabled.
Does anyone know what could be causing this or if Marketo is just not supporting video?
Please let me know!