Is it possible that someone else used your email address to register on the site? Maybe by mistake or on purpose? Sometimes I get similar messages as if I registered on some site, although Im sure it is the first time I have even heard of them.

Although, it is much more likely that this is a dirty and scam tactic to lure new victims. Your email was probably picked up from some leaked database circulating online. In that case, that casino should not be trusted at all.