You cannot claim to be someone else - i.e. identity theft, but there is a big difference in truely claiming to be someone else and putting in names in chat rooms etc, that are not your real names. Simply put you may wish to use initials in the future and thus not use anyones particular name. I would stop talking or responding to the email and change your email address.
NOTE: This is not intended to be legal advise. You may wish to talk to an attorney of your choosing if you want legal advise.