As you already know, Gmail has been redesigned and its changes are not just about its appearance. OR Google e-mail service, has acquired new features and is going to gain more with the weather. For example, we'll soon see a predictive text feature that will allow you to select suggested words to automatically populate a message.
But for now, the new feature that's already available is the confidential operation of Gmail or Confidential Mode.
With confidential mode in Gmail, the email you send will be able to expire after a set period of time. By default, this time period is 1 weekteam, however you can set a different expiration time.
A message with confidential content has an extra level of security: The recipient must enter a passcode sent to him by SMS to read the message. The availability of this particular feature is not available globally, and therefore can not be used by everyone who has the confidential feature in Gmail. In Greece it works without any problems.
Let's see how it works:
Open Gmail and click on the new message at the top left. At the bottom, you'll see a new padlock icon with a clock. Click
A new window opens where you can set the end of the message.
There are predetermined time periods. one day, one week, one month, one year and five years.
To add a password, select the “SMS Password” option. If your message has more than one recipient, you must enter a phone number for each recipient. THE Password SMS is the code your recipient needs to unlock the message sent to the phone number you add, so make sure it's correct.
When you tap Send, and use the SMS function, a new window opens to add the recipient's phone.
After adding the phone number, you can send the message.
That's it. You can send the message and if you want, you can undo it within 30 seconds. Αν αργότερα καταλάβετε ότι έχετε στείλει το μήνυμα σε λάθος άτομο, μπορείτε να κάνετε κλικ στο button Revoke access to the sent message and the recipient will not be able to open it. 
Confidential emails do not open in Gmail. You will receive the message in Gmail, but when you open it, you will need to click a second button to see the message in a new tab (see the picture above).
If you block access to a message, the email will not disappear from the recipient's inbox, however, when it clicks on the View the email link, Gmail will inform it that it does not have access to the message.
Access to a message is abolished indiscriminately for all recipients of the message. You can not revoke access to a person and allow others.
