We are 100% sure that you all use Gmail. Recently, Gmail gets a new UI. Announced by Google at Google I/O 2018 event. In April Gmail received Gmail Confidential Mode for Desktop Users. And now this is making its way to Android and IOS Users. This is a default feature that you will get. If not, you can try this, Enable Gmail New Features. Hope this would help you.
Google keeps on enhancing its products to meet every need of the user. In this Series, Google provides Gmail Confidential Mode for users to somewhat encrypt their Emails. This feature let the sender set a time period on the Email. Time period? Basically time period here acts as the period of authenticity. Time period provided by the Sender, let the receiver to do anything with Email. After the time period, he/she (receiver) cannot do anything with the Email. The email will act as a died Email nothing can be done except viewing (or the Email will be deleted permanently).
Time Period can be anything from 1 day to 5 years. A user can choose any duration. There is another option. The user can choose passcode for double security. Passcodes are generated randomly by Google. The receiver will get an email asking for the passcode. This Gmail Confidential Mode works same on both Android as well as iOS. Gmail users (receivers) will directly get the Email whereas non-Gmail users will get a link for the Email. They have to visit the link and provide the passcode if provided by the sender in passcode mode.