Yahoo has been a little slower to the encryption party than Google. But yesterday Alex Stamos, Yahoo's chief information officer, announced at the Black Hat security conference in Las Vegas that Yahoo Mail will be encrypted end-to-end by some time in 2015. Not just that, it'll be done in such a way as to make it compatible with Gmail's, too.
Yahoo's encryption, then, will mean that all email sent between the two services will be fully encrypted, end-to-end. Given that more than 425 million people use Gmail, and Yahoo Mail usage estimated at 273 million, that's a lot of extra security.
When two such large organisations join forces on something like this, you know it's important, and Yahoo has "the hope is that this is open and will be adopted by many others in the email ecosystem". Which sounds like a great idea; let's hope end-to-end soon becomes the norm. [WSJ, CNET]