Does your ISP allow you to send mail out via port 25? Many ISPs don't.
Also, note that if you have a dynamic IP from your ISP, many servers won't accept mail directly from your server, you'll have to use your ISP's mail server as relay host.
Postfix will almost work out of the box in Fedora these days.
CentOS wiki and ArchWiki both have articles. The CentOS one is using it in conjunction with Dovecot, but is still pretty good.
The ArchLinux one might also be useful.