You opened a nice box of worms. :-).
Just because you have a static IP address does NOT mean that you have to host the mail service on a local server.
Maintaining a server is quite tricky and IF your ISP is really shutting down the Mail service for your domain you should consider google apps www.google.com/a to give you 24/7, 99.99% uptime mail and other services.
If you would like to dig into running your own server, you have to have a Mac, which will be up and running ALL the time and connected to the internet. Then with your fixed IP you make one nameserver entry in your controlpanel of your ISP.
Then you follow the manual http://help.apple.com/advancedserveradmin/mac/10.8/
to set up your server and it's possible services.
hmmm thanks but I was expecting a more detailed step by step guide. what part of the manual am I supposed to look at exactly? I dont have time to cover it all
Yes, the server WILL be running 24/7 and connected to the net always, its for the company I work for.
I didnt understand this part you said:
"Then with your fixed IP you make one nameserver entry in your controlpanel of your ISP."
Makes no sense to me. ISP? Did you mean the Server app?
What services need to be turned on/active in the Server app? DNS? Open Directory? etc. and how do I set them up?
I saw some names like: server.g0mini.private as the name of my server. I didnt even make that name, I guess it automatically made it. What does this even mean? I never seen a name like that before with server at the beginning and private at the end. g0mini = ? G0 is our adiminstator account name on our mac mini which the server is being run off, so I'm guessing thats how it came up with this shortname.
Also, do I set up my server as local, local +VPN, or local +internet?
And in the Mail service panel of the Server app where it says "Provide mail for:" what do I enter in here?
really, the manual IS a step by step. Fully Qualified Domain Names get covered, how to set up A-Records at your ISP so that yourserver.com resolves to your fixed IP and all the rest.
Dig into it and then come up with more concise questions, which we/I can gladly help you.
Based on your questions you have to start with "fundamentals". It is really very well written.
Just one "opinion". If you set up your first Server in your life, you go online right away having users depend on the data served, you do not know somethings about DNS, A-Records, MX-Records, SSL and then you have your whole team looking at you when email is down.... is a recipe for sleepless nights.
I would strongly consider hiring a consultant for you first try, or leave such a essential service as "email" onto your ISP or google apps, until you have the server up and running with filesharing, calendars, website or whatever service you might offer.