It surprises me how few people actually do this, it's something I've been doing for a while.
Create a new gmail / live / yahoo / what ever free email account. Name it something specific like "[email protected]" (assuming unholy is your first name). Easy to remember and easily identifiable (if you use like 6-7 email accounts daily like I do).
Go to Battle.net and change your registered email to the [email protected] email account.
All you need to do now is never ever enter that email anywhere but on the official gmail site, battle.net site or in your wow login screen. It's impossible for anyone to ever then send you spam or scam emails unless you have a keylogger and so on.