The Revenue do not send emails to tell you that you have a rebate. It's a scam. I get them all the time. Be careful if you have clicked into this site as some of these scams try to get access to your computer though you clicking into them.
Go to the H.M.Revenue website where you will see a warning about these scams they also give you an email address to send scams to so they can deal with them.
If you suspect a scam, click into "File then Properties then Details then Message source" at the top of your page, it will give you exactly where the email came from. Often you see it's coming from abroad, last one I got came from Denmark. When you report these scams you should send a copy of the "Message source" with the original mail. I always do.