How can i get outlook express to forward a copy of my emails to yahoo email?

I tried using "rules" in express but it only gives me the option of forwarding all my emails to another email address - I want to actually just receive a COPY.
How can i get outlook express to forward a copy of my emails to yahoo email?
Unfortunately, I don't think there's a way to send a double to another account using outlook express, and forwarding is your only option.