[CentOS] Pointer to simple mail server setup?

Hello.

I need to set up a mail server for a small (~5 people) organization on 
CentOS 5.1.

While I am very familiar with CentOS and Linux in general, I have zero 
experience in setting up a POP3(s)/SMTP mail server.  I suppose 
eventually I'd like to do spam/virus filtering, but initially the simple 
sending/receiving of mail will be adequate.

Can someone point me to a tutorial on setting up a mail server on CentOS 
5?

Thanks.