DNS propagation and internal network

Hi guys,

I recently changed my IP address to a domain name, I went through the 3 days of propagation, but what I have found is that the mail extension to my domain name cannot be seen on the inside of my own network. It can be pinged and looked up from other computers, but it would appear that my internal DNS does is not aware of the change, so mail clients constantly return an error that the host name cannot be found.

Can anyone point me to a simple but effective solution to this problem?

I am running Windows 2003 Server, and using a 3rd party domain host (IXWebhosting.om).

regards,
Michael