Dating site spam mail?

My boyfriend keeps getting emails from dating sites, one in particular. When i clicked into the email i followed the link and was brought to the site and discovered that there was an account set up in his name i wouldn't be so suspicious only his date of birth on his profile was the correct one and other details were right too. he denied it of course and says he doesn't know how they got his details. i don't know weather to believe him or not. is he lying??