Source: Google
Google is finally bringing end-to-end encryption to Gmail. But it will be for Google Workspace and education users. End-to-end encryption “ensures sensitive data in the email body and attachments are indecipherable to Google servers. Customers retain control over encryption keys and the identity service to access those keys.”
You can apply for beta access to test the feature through this link. Google requires that both the sender and the recipients have end-to-end encryption turned on and valid certificates. You won't be able to send an email if any of the recipients are missing a valid certificate.