mail stuck in outbound queue

Dear all
I wonder if any of you guys and gals can help me out.
I have set up a small email network using windows 2000 with exchange 5.5. I have a public DNS MX record set up and a linksys cable router to forward all port 25 requests to my exchangeserver. The mx record points to the public IP address given by my ISP which is currently the router. The system recieves email okay to my domain. However when I send out email it gets stuck in the outbound mail queue. Now I know this would happen ifthe DNS is not correct. But I have added the correct DNS suppiled by my ISP. So not to sure what to do next. Any help would be appreciated. Any exchange guru’s out there?????