Google is Testing Self-Destructing Emails in New Gmail (techcrunch.com)
The upcoming update to Gmail might include a feature which would allow users to send emails that expire after a user-defined period of time. From a report: Working on an email service is hard as you have to be compatible with all sorts of email providers and email clients. But it doesn't seem to be stopping Google as the company is now evolving beyond the simple POP3/IMAP/SMTP protocols. Based on those screenshots, expiring emails work pretty much like expiring emails in ProtonMail. After some time, the email becomes unreadable. In the compose screen, there's a tiny lock icon called "confidential mode." It says that the recipient won't be able to forward email content, copy and paste, download or print the email.
As a real lawyer, I use screenshots all the time. Usually, I use them with text messages and Facebook posts, but I could see it working here too. The courts I am in front of allow screenshots because a lot of time, they are the only evidence available in a way accessible to the Court. The thinking of the courts is that you want the best evidence available to be what is admitted. If you don't have the better evidence but have a good reason why, they will let you do so.
You cannot haul your cell phone provider in front of the court for every little dispute, nor can you bring Apple, or Facebook, so they let in screenshots. In the case of emails, they prefer printouts with full headers but not everyone knows that so in small claims, they will allow lesser evidence in.
In this case, because the email, by its nature, destroys itself, screenshots are all that would remain of said email. Therefore, the best evidence available to a party is the screenshot, so if the disagreement is about the content of the message, then screenshots will almost have to be admitted if the actual content is in dispute. No better evidence + Good reason why == admissible evidence. Of course, all this assumes there are no other objections to the evidence (relevance, hearsay, privilege, etc.).