not able to send email from newly setup Exchange 2003 server

Hello, all:

I recently setup a new additional mail server (Exchang 2003). I have 2 exchange 2003 servers, still running. A couple of weeks ago, i changed MX record from one of the old server to this new server.

After change, we are able to receive emails. But we are experiencing problem sending out mail. sometimes it works, sometimes it does not.

I did some troubleshooting with winroute.exe. i noticed that there is an error message for the new server" Object not found in Active Directory", but this new mail server is joined the domain as a member server.

Any help???

Richard