Google has added a feature in its mail applications that will enable users to send messages and attachments with ‘Gmail’s confidential mode’ to help protect sensitive information from unauthorized access. You can use confidential mode to set an expiration date for messages or revoke access at any time. Recipients of the confidential message will have options to forward, copy, print, and download disabled.
From Google’s published text on the subject (link below):
Although confidential mode helps prevent the recipients from accidentally sharing your email, it doesn’t prevent recipients from taking screenshots or photos of your messages or attachments. Recipients who have malicious programs on their computer may still be able to copy or download your messages or attachments.
Please note that this feature isn’t available for G Suite customers at this time.
More at: https://support.google.com/mail/answer/7674059