This is a very common e-mail many including myself have been getting. Always hover over the link to see where it directs to, and look for the green bar next to the URL that tells you you're "secure." NEVER enter your information.
PS. Jagex will use Message Centre if they need to contact you - not your e-mail.
As long as you don't put in anything you'll be fine. A good way to test these sites out is just putting in something like "sjdfhjklasdhf" in the username and password and seeing what happens.
lol some1 took a lot of time to make that site its dead accurate one even has it matching identically copyright info only thing is sad kids on here are emailing em out to people