MySQL query sorting help

[skylab001]

I was curious if there is a way to sort out duplicates in data returned by an query. I have a database, basically a mailing list database and when I query the database for the emails addresses, I get the returns echoed to the page as expected, but it looks like some people have signed up multiple times. So I have duplicates in my echoed list.  Is there a way to have the data sort so the duplicates do not appear, and the email will only appear once on the list? I don't want people to be getting 5 of the same emails from me.

[Barand]

SELECT DISTINCT emailaddress FROM mailing_list

[darkfreaks]

<?php
mysql_select_db("db",$connect);

$numrows= mysql_num_rows($query);

if($numrows>1) {echo 'sorry but this email adress is already in use'; 
$query='DELETE FROM users WHERE email='$email'';}?>