A family of Microsoft presentation graphics products that offer tools for creating presentations and adding graphic effects like multimedia objects and special effects with text.
From your description, it sounds as though you have Active content in your presentations. As long as that's the case and your clients' systems don't permit the email, all you can do is make sure the active content is removed before sending them email or arrange some other way for them to receive the files; links to OneDrive or the like, perhaps.