How could i keep my hide the email adress for the sender in yahoogroups ?

i meen when amember send an email i dont want the resever of the mail can see the sender email adress

How could i keep my hide the email adress for the sender in yahoogroups ?
It's quick and easy-----click on the arrow beside forward and choose "as inline text". The window is activated. Highlight the senders address and press the delete key on the keyboard and it's gone instantly.