If it's only "please confirm your account" and password reset emails then the user probably just mistyped the email address. If their username is go-to-ydotcom

If it's only "please confirm your account" and password reset emails then the user probably just mistyped the email address. If their username is go-to-ydotcom-for-free-cash then it might be spam. It doesn't seem very effective but I know a company where a spammer created 10.000 accounts overnight to be sent to random people.