unSend.it allows users to unsend or edit any email after it's been sent (even after being opened by the recipient). It can remove all content from the body of the email (including any attachments) you sent. The email itself will always remain in your recipient's inbox along with the subject line – however, all email message content will be removed.

there's been a few products claiming to do things like this. unfortunately this product doesn't explain any of the technicalities about how they would achieve what they claim (revoking attachments etc). I would presume that the email just links to the attachments or they modify the email content in some way, i.e. changing the text to an image.

The video implies you can undo a "Reply-All" when you meant to do a "Reply". But I'm guessing you can only delete what is loaded in the body via html, so the person you accidentally "Replied-All" to would still get an email from you, just with a blank body?