Earlier quoted context omitted.
This. Email messages are digital postcards. When it leaves your computer (house) and goes to your ISP (local post office), anyone at that place can pick it up and read it before sending it on its way to the recipient's mail handler. While it's in transit, it's not sealed, it's not obscured or encrypted, it is plain text. Now, that doesn't change the fact that Yahoo rolled over like a puppy when the government came ca…
Don't a lot of the big providers pass emails between each other encrypted with TLS? And emails internal to Yahoo's email system wouldn't be visible to your ISP or anyone outside of Yahoo. https://www.google.com/transparencyreport/saferemail/
[1] https://www.google.com/transparencyreport/saferemail/faq/#wh...
[2] http://arstechnica.com/tech-policy/2016/10/report-fbi-andor-...