[exim] iptables

Where within the EXIM directory, and sample script, should I install
iptable (replace 1.2.3.4 with IP to allow) rules to block ports 25.

Sample of iptables rules:

iptables -I INPUT -p tcp -s 1.2.3.4 --dport 25 -j ACCEPT
iptables -I INPUT -p tcp -s 1.2.3.4 --dport 25 -j ACCEPT
iptables -I INPUT -p tcp --dport 2525 -j REJECT

iptables -I INPUT -p tcp -s 1.2.3.4 --dport 25 -j ACCEPT
iptables -I INPUT -p tcp -s 1.2.3.4 --dport 25 -j ACCEPT
iptables -I INPUT -p tcp --dport 2525 -j REJECT


And, is this the best policy to block port 25?