Dmail launched today and seems intriguing. Using the Chrome extension, you can send emails that can later be "deleted" without the recipient needing special downloads to read. I've seen similar products before, but those rely on turning text into images.
Per the founder, on Product Hunt: "In all seriousness, we do not use images, only text. I can't give away exactly how we do it, but I will say we use a series of authentications and encryption, and that neither Dmail nor Gmail ever gets a full copy of the content of the email. Don't you love riddles?"
So how does it work?
Note this quote from Cory Doctorow:
"For DRM to work, you have to send a scrambled message (say, a movie) to your customer, then give your customer a program to unscramble it. Anyone who wants to can become your customer simply by downloading your player or buying your device – "anyone" in this case includes the most skilled technical people in the world. From there, your adversary's job is to figure out where in the player you've hidden the key that is used to unscramble the message (the movie, the ebook, song, etc). Once she does that, she can make her own player that unscrambles your files." http://www.theguardian.com/technology/blog/2014/feb/05/digit...