Set Up to send and receive Mail from other Domains like live.com,gmail etc, Exchange 2007 SP3

Hello,
Hope you’re having a good day there,
I just finished setting up the Microsoft Exchange Server 2007 SP3, WITH 2 DC 2008 R2, the exchange 2007 SP2 is install in a member server not in a domain controller and  this is the first time I have configured/ setting up the exchange server. Am not sure about one thing here and I need you guys to help me out with this.
Now after I have completed the installation and the configuration of the exchange server.am not sure which IP address or DNS should be pointed in the Go-Daddy account to forward emails
My Network is setup in Virtual Box I have them all running on PFSENSE
Router setup with IP scheme 10.0.0.x ( router is comcast and has a public Ip totally different) my router is setup with 192.168.1.2 for the client machines. I have Virtual servers running on this one for AD and one for exchange. I have used static IP for both the servers with 10.0.0.1 and 10.0.0.2 for AD and 10.0.0.3 for exchange. Now should I be pointing my exchange IP ie 10.0.0.3 in my go-daddy to create an mx record? or wich one should I use!!


Please guide me in the right direction

Thanks in advance, looking forward for a resolution

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Efra Riv