Exchange Smtp problems

we have installed a new site in our exchange organization and are trying to connect via smtp. Everything appears fine, connection is established replication begins and after replication progresses, the new site cannot send smtp mail. It tries to send thru the main corporate server and not through its own smtp server. internal e-mail works from site to site but smtp mail out from the new site doesn’t work. Have tried changing route costs to no avail, what else???