Background checks and Internet companies

I recently applied for a job in a big internet company and attended the interview. I use hosted email service of that company. I own multiple email id's and use them for different purposes.

Today i received a notification in my primary email address that, "You are subscribed to xyz" group. But i didn't subscribe to any xyz group. Some one did on my behalf.

I believe they are doing a background check on me by connecting different email id's.

Is it legal? Any one experienced same kind of behaviour?