Restrict login to Email address only

 Hello, i have an E-commerce website and i manage my users with the help of S2 members, and in the same a form in the website for the same Users.

The problem is that the users Comment on threads and that’s allow other users to see their Username in consequence that mean that other user have the half of the Login details so that causes a risque for their accounts to be hacked, that’s why i whant to allow Login with the Email address only (Not using the Username).
Can you please help me.
Thank you in advance.

s2Member just uses the regular WordPress login form. So any plugin that allows users to login only with their email address will do what you want.