I need to install a linux mail server at an office, I have Redhat 7.2 It must work like this
the linux box must grab the mail from the isp i.e pop off it, it must dial out every half hour, then it must
transfer the mail into the users mail box or they must pop off the linux box.

How would I go by doing this , which will be the best way and what utilities or programs do I need to use
and install.

Pls Help
This is a first for me I have never set up a mail server like this in linux

Well I am still pulling out my hair trying to get my own mail server setup, but I can give you a the names of a few programs that you will need, I found this out with all the reading I have been doing try to get my own server working. The program you are looking for that will retrieve your mail from your ISP is call Fetchmail (Correct me if I am wrong please), I believe in this type of setup you will also have to have an smtp daemon. I switched from sendmail to postfix as I found it to be alot easier to configure. As for your users retrieving their mail, what type of retrieval system do you want to use? POP, LDAP, or local folders? I am still having problems myself getting my POP daemon to retrieve users mail from their mailbox, so I can not recommend anything for you there. I believe if you goto postfix.org they have some info in their FAQ's about this type of setup.

Goodluck!