Google now encrypts all Gmail messages moving internally on its servers. The company made HTTPS the default with its Gmail service back in 2010 and then, later, did the same with many web queries using its own search engine. The changes announced Thursday will make it tougher for snoops be they the NSA or hackers to pry open Gmail sessions. But it doesnt cover data traveling between services from one email provider to another, for instance, for example. Google, like any email service provider, is compelled to hand over data whenever government (legally) tells it to jump.”]
Source: https://nakedsecurity.sophos.com/2014/03/21/google-switches-gmail-to-https-only/