You must admit this one has an authentic look and feel. Most that I've seen are laughable by comparison.
Plus, there are plenty of legitimate people on the internet who send you links to domain names different to their main one. I think Amazon have done that to me. I never follow the links. But when respectable companies do that to you, how can you tell the honest people from the conmen?
EDIT> Specific example. I have an email from Argos, a popular chain of UK stores whose website is
www.argos.co.uk. The email is full of links to
www.email-argos.co.uk. I believe the email is legitimate, but I wouldn't dream of using the links on principle, because the site is not the same one that I know for certain is theirs.