Gmail’s new security indicatorsFebruary 11, 2016 – 5:32 AM
Google added two new security indicators to its email service Gmail which reveal TLS encryption support and whether the sender could be authenticated.
Many popular email services, including Gmail, support TLS (Transport Layer Security) encryption to protect data while it is in transit.
TLS is only useful if both the sending and receiving email service supports it, and one of the new features highlights on Gmail when TSL encryption is not supported by another service.
Gmail highlights the fact with a red open padlock image in the email header. You can click on the lock icon to display additional information, but it means effectively that the third-party mail server did not encrypt the message (likely because it is not configured to use TLS).