As Linc Davis states, yes.
If it's your goal, then you're going to learn about IP, DNS, backup and various other topics in the process.
www.example.com can serve mail (and web and...) just as well as mail.example.com, if that's where the MX record points, and if that's an A record.
Mac Pro is likely massively overpowered for these sorts of tasks; you probably can't afford a network connection that'll big enough to even keep that box mildly busy.
You'll also want static IP service from your ISP; a business-tier connection.
As an alternative to running your own, hosting services are cheap, and they deal with the hardware and the software for you. (Not that I intend to try to talk you out of this, just that you can pay for multiple years of service for just the cost of a Mac Mini Server box alone. That's also before you consider the cost of the network, and of your time and effort, too.)
I am in the process of learning all TCP/IP ideas and topics, it just takes a little bit to get my mind wrapped around it in context.
Ya i know im being complicated and thats on purpose. Im an IT student and the point of this server isnt to acctually use it but use it to show that i can do it and put it on a resume. So in short, Im being complicated on purpose.
Im going to be working with a Dynamic DNS so that i dont have deal with my ISP. Our bill is balancing on a razors edge so i dont want to screw anything up (its my parents house so i dont have too much of a say in it anyway).