Ray Kurzweil championed the translating telephone. It sucked back then and it still sucks now. Computer translation leaves too much to be desired, and what's more with a system like this, people could be tricked into reading erroneous translations without knowing better. Chances are that if you receive e-mails in multiple languages it's because you have interacted with a website, service in that other language (implying that you understand it) or said e-mail is simply spam and you don't care what it says anyway.