That's definately a spam email. I get loads of them to my other yahoo email.
As a general rule I would either look at the properties of the email (preferably without opening the email) to check the links and urls, or just log manually in to your account via the web browser.. if there is anything to update or upgrade then it'll show up in there.
This is the problem with using an outside free email service like yahoo. It's open to attacks of all kinds from anyone.
Demon => Freeserve => Pipex => Be => Sky => BT Infinity 2