Qmail configuration problem

[shajain]

Hi, Four of my sites are connected on VSAT network and I am using qmail-Linux m/c at all sites, one of those four is a central relay server. Now the problem is I want to configure foo.com domain which should work like this : for locally configured users it should route locally and for the same domain name(foo.com) if the user is not configured locally then it should go to the remote relay server. If I define foo.com in locals then it sees that all the users(whether it is for local or remote) it is taking that as locals only and if i define bar1.foo.com, bar2.foo.com in locals for different sites it takes all the mail account as remote and for local users also it is travelling upto the relay servers and then going back. Any help highly appreciated. Thanks, Shailendra.