Setting Up Server Mail To Actually Work?


I've been using mac server for some time now with great success. Up until now I've been using just a few of the simple things. Contacts, Calendar, Messenger and the Website. I use the server as kind of a background service. Now I'm looking to move mail into the mix.... So far I've only been able to get it to work on the same subnet and only to people inside the user group. Ie I can't mail some one who doesn't have a address.

I'm using GoDaddy as the DNS host. Can someone provide me with direction to get me moving.

The reason Im wanting to move from a hosted email service to a self served email is that we are a growing but small company and I don't want to pay for hosted email address. GoDaddy gave us 10 email address. But they want too much to add more. I figured the easiest way was to just host my own email.

I also like to do things I've never done before and just want to learn!
I've watched them over and over. and while he does an amazing job with all of OS Server he glazes over mail. he doesn't even truly set one up he just acts as if he does and then moves on to say "don't set one up..."
Have you correctly set OS X Server's DNS settings for your domain name?

Have you properly configured the MX records via GoDaddy's control panel to point to your OS X Server's public IP address?

Mucking about with DNS is both interesting, confusing, and not for a novice (because one wrong setting can have catastrophic consequences). Are you familiar enough with DNS to do these things? If not, GoDaddy's technical support can be very helpful.