ZMAIL allows users to send emails that will expire ("self-destruct") after a set time. This development is designed to improve security, comply with the organization's document retention policy and, ultimately, avoid messages being used in the future to haunt senders.
ZMAIL also allows users to set a release time for the email, preventing the message to be read before a pre-defined date, and restricts who is allowed to read an email. These features can be used together with the ZMAIL expiration time, by governments, companies and individuals to prevent leaks of sensitive information.
How does it work?
ZMAIL timestamps every email that is sent and, when ordered by the user with a command to set an expiration time, defines a lifetime for the decryption key for that email. In addition to a logical block preventing an expired key to be used, the key is physically destroyed after its lifetime expires. This effectively makes that email permanently unavailable after the set date. Even if the email is still retained on the sender's or recipients' computer, and in corporate networks copies or back-up tapes of mail servers, the email can no longer be read.
With ZMAIL's self-destruct email feature, the sender is able to unilaterally enforce what amounts to copyright limitations on reading the email. This also helps the recipients, who no longer have the burden to destroy the emails -- which might create legal difficulties either way (destroyed or not destroyed) according to the recipient's local laws and rules on shredding documents (that might differ from the sender's local laws and rules).
Read more about the Expiration Time.