Ask HN: How does DMail change the text of an email?

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?