postfix smarthost to relay in same domain

[str.tux at gmail.com (str tux)]

Hello List,

In our domain I got an existing mail server (Domino Server) and I
setup another mail server using postfix using centos4. Due to some
license issues for Domino, I want to use the new postfix server in
adding new mail users - but still maintain delivery between the two.

I have no much problem since in Domino smarthost settings are available.

But I'm wondering, where such settings in postfix?

Please guide me accordingly.

Regards,
str