It has been revealed that "Yahoo last year secretly built a custom software program to search all of its customers' incoming emails for specific information provided by US intelligence officials." It is not known what the "specific Information" is/was. It is believed that this is the first example of a US internet company agreeing to a spy agency's request to search all arriving messages, rather than just examining stored messages or just scanning a targeted few accounts in real time. If this concerns you and you have a Yahoo mail account there are plenty of other options out there. For example, Tutanota provides a free end-to-end encrypted email service along with iOS and Android apps.
from The Universal Machine http://universal-machine.blogspot.com/