Weeding out duplicates

[Jonathan Duncan]

I am trying to get rid of duplicate user info entries in a database.  I
am assuming that the email address is unique but other information, like
first name, last name, address, etc are not.  The "email" field is not a
unique field in the database.  I was trying something like the
following, but not getting what I wanted.

select distinct u1.id,u1.firstname,u1.lastname,u1.email from Users u1,
Users u2 where u1.email=u2.email;

How can I go about identifying the duplicate entries of email addresses?

Thank you,
Jonathan Duncan