Users can help protect sensitive information from unauthorized access using Gmail confidential mode. Recipients of messages in confidential mode don't have the option to forward, copy, print, or download messages, including attachments. Users can set a message expiration date, revoke message access at any time, and require an SMS verification code to access messages. Learn how to send/open confidential emails here: https://support.google.com/mail/answer/7674059 More info. can also be found here: https://support.google.com/a/answer/7684332?hl=en
Important: Although confidential mode helps prevent the recipients from accidentally sharing an 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 be able to copy or download your messages or attachments.