Forward Email for one account to another domain?

I apologize if this is a repeat question, but I am still having problems setting this up. Snow Lep used to have the ability to forward email for a user to another location. I host my own domain with multiple users. I want all mail sent to one of those users, in my domain, to go to another email address outside my dowmain. Basiclly to do whatever process they "Forward mail" option in old Workgroup Manger, for a user.

I looked into the "Virtual Domain" stuff for postfix, and forwarding there, but from what I can understand, thats for Virtual Domains, not for ones that your actually hosting. i.e. Can't have domain.com in Mydestinations AND Virtual file.

So how do I acomplish this?

Thanks in advance.

Steve