postfix as mail relayhost

[piti]

hi

i am planning to setup my postfix as relay host
i know what to change in the transport table
what i ned to know is:
if a mail comes for useralias, that is now, according to my postfix config, delivered to user, to what address would it be delivered on the target mailserver, to useralias or user?
i don't know if i need to config the target mailserver also for the aliased addresses

thanx