And, indeed, that sort of functionality runs counter to the idea that once something has been sent to me, it's "mine" to keep/delete/whatever without someone else having the ability to change or delete it without my permission.
You have no idea how much some managers love this idea.
I know I had a former boss that loved to try using the outlook "unsend the stupid thing i sent" feature.
Little did he know the cients could turn that bit of functionality off. He hated when we replied to the emails he had "purged".
in order to do that, you can send an unique link as content so you can have total control over what you sent. doubt that many would click but i couldn't think of any other way.
other than that, i don't think receivers like the idea that others can control what's in their inbox.
Well there is https://www.criptext.com/
I think certain enterprise-y email solutions have this, but there's no way to have that happen in the distributed email ecosystem unless all your messages were just links to a website that could delete the content centrally, or similarly, jpg's of rendered text that were somehow forced to be remotely fetched each time.