Opening Ports in Linux

Follow below instruction

# vi /etc/sysconfig/iptables
-A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp --dport 80 -j ACCEPT
# /etc/init.d/iptables restart

Verify that port is open 

netstat -tulpn | less  

Make sure iptables is allowing port 80 / 110 / 143 connections:
iptables -L -n