Gmail – Gmail to Gmail Email Security

gmailSecurity

Consider an email sent from <some_user>@gmail.com to <some_other_user>@gmail.com. Aside from the HTTPS encryption that each user has with the server, I presume emails have to be stored and often exchanged between Google's email servers.

Are these communications encrypted?

For example, my understanding is that content sent with SMTP without SSL is sent in plain text, making it relatively easier for any eavesdropper / man-in-the-middle to see the content of the communication.

What protocol does Gmail use to in end-to-end communications between Gmail users?

Is it known to be encrypted (even if minimally) all the way from client to client?

How "safe" does Google officially claim these communications are?

Best Answer

From the official Gmail blog dated Thursday, March 20, 2014 at: http://gmailblog.blogspot.com/2014/03/staying-at-forefront-of-email-security.html

In addition, every single email message you send or receive—100% of them—is encrypted while moving internally. This ensures that your messages are safe not only when they move between you and Gmail's servers, but also as they move between Google's data centers—something we made a top priority after last summer’s revelations.

Google also provides a page where you can check which providers support email encryption in transit (between domains): http://www.google.com/transparencyreport/saferemail/#search=gmail.com