There's a new "confidential" toggle on the web Gmail (at least for gapps accounts) that let newly composed email expire after a certain amount of time. Not avai

There's a new "confidential" toggle on the web Gmail (at least for gapps accounts) that let newly composed email expire after a certain amount of time. Not available on Android Gmail yet. Just saw it yesterday. The actual email to non-gmail addresses is just a link to fetch the mail body, which can be validated with SMS.