LDAP authentication using email address

[Gokul nath]

Hi,
I have configured openldap and it is working for username and password 
authentication.
How do i make my email address as login id in LDAP? 
my working scenario is below.
User : user1, user2Group: Group1, Group2
I have added user1 to Group1 and done apache authentication using Group1. Login 
is working if i add any user to that group. i would like to make email address 
as login id. Please suggest how to configure the same.
ThanksGokul