Is the email for your account is yahoo.com or yahoo.cn ? if so then its legit, so basically yahoo is kinda forbidden or blocked now. I don't know whether its by the netease company or chinese government but basically they asked you to change your email address into non yahoo. Make sure though its a legit email and have a blizzard logo.
I also got that email since 1 month ago, but the problem is to change the email you have to own a copy of the Id card that you use to register the account. If you don't change the email it won't change your gameplay and stuff, but if you got hacked and stuff you can't do it because your email address is invalid.
P.S : Please tell me if somehow you got the GM agree to change your mail w/o the damn copy >.>