My advice: Assume suspect until otherwise proven.
Normally a company like Blizzard would address you by saying things like "Greetings <
your name & account handle>". Also they would strongly recommend going to their website in another browser and not in a hot link.
Finally: Use common sense. If you have done nothing wrong, then you have nothing to worry about. Blizzard isn't going to just randomly select you for an investigation. Just forward the email to
[email protected] and they will tell you if it is legit or not. Odds are good it is not.