Send Connector?

I’m running E2K7 SP1 on W2K8SP2 (both Enterprise) and have a routing problem. I host multiple domains but need to send outbound email for one domain to a separate smarthost. I thought I could do this with a Send Connector however it doesn’t seem to work as expected. Can anyone help?

Domain         Smarthost
abc.com          1.2.3.4
def.com           5.6.7.8