I haven't bothered to learn howto do it myself since I use my isp's E-mail stuff, however
Linuxdocs.org is good place to start looking.
Also if you snoop around Redhat's website it probably give you some tips on how to do things.
Do a search on google.com fo stuff like:
E-mail linux howto
linux mail server howto
redhat mail administration etc etc....
you get the idea.
It's doutful that anyone will tell you exaxctly what to do in order to do something. Forums are better for asking specific question about stuff that doesn't make sense or you can't get to work properly. There are many resources out there that will attempt to teach you about pretty much every aspect of using Linux most people are not willing to reply specificly to questions with so many good resources out there.
Good Luck!