I replaced an old exchange server 2000 box with a new server with exchange 2003. My problem is that to access the owa on the old box you would type webmail.mydomain.com/exchange. I used the same ip address that the old box was using on the new box so I won't have to call my ISp. Now I can't access the new box with the old owa address. What do I need to do so the the new box responds to the old OWA url?

The above problem was solved. Now I can receive any external emails. I can send email within the organization and to external addresses but the system is not receiving any emails from outside domains. Any ideas on how I can solve this issue?

If you can send out, and exchange users can send to other internal exchange users, it sounds like you have improperly configured MX records in the public DNS namespace. I know you said you used the same IP, but something isn't lining up. Go to dnsstuff.com and put in your domain and do an MX record lookup. Make sure it has the right hostname. Then use dnsstuff.com to resolve that hostname. Make sure it maps to where you think. Then make sure you have port 25 properly configured on any firewalls you might have. Im suggesting dnsstuff.com so that you can ensure you are looking from an outside point of view. You might have internal name resolution or IP distribution confused with external. What is the NDR (bounce back) external users get when they try to send to your users? The answer often lies here.