And people think MIME is a secure, authenticated protocol to begin with? Lol. Any server your email goes through can read it's contents and use it for whatever.
Google provides their service through content scanning emails, and yes, they openly admit to delivering content to the NSA. The NSA is the least of our worrys when it comes to our email content leaking. If you want secure messaging, don't use email, or use a email service that ensures privacy.