If you’re sending confidential information by mail, you wouldn’t put it in a postcard. And if you want your email to be protected from snooping, both you and the people you’re emailing with need to use services that support encryption in transit.

Emails sent between Gmail users are encrypted as they move between Google's data centers—but about 40 percent of emails sent between Gmail and other providers aren’t encrypted. Learn more in a new section of Google's Transparency Report: