NOT insert existing record

[[EMAIL PROTECTED]]

I have a table like this :
+-------+----------+------+-----+---------+----------------+
| Field | Type     | Null | Key | Default | Extra          |
+-------+----------+------+-----+---------+----------------+
| id    | int(11)  |      | PRI | 0       | auto_increment |
| isim  | char(26) | YES  |     | NULL    |                |
| email | char(30) | YES  |     | NULL    |                |
+-------+----------+------+-----+---------+----------------+

I take email address from web with php..
I want to control inserting email address..
I want to insert the same address only one time.
my code:
...................
mysql_connect(.............) or  die("veritabanina baglanilamadi");
mysql_select_db("db_edakom");
$result = mysql_query ("select * from email2");

if  ($email == mysql_fetch_array ($result)) {
        echo "Bu email adresi daha once girilmistir.";
        echo 'tekrar denemek icin <a href="javascript:history.go(-1)
>tiklayiniz.</a>';
}

else {
$query = "insert into email2 values('', '$isim','$email')";
mysql_query($query) or die("Cant insert data!");
print "Islem tamamlandi";
mysql_close();
     }

HOW CAN I DO THIS?

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