sudo iptables -I smtp_out 1 -p tcp -s 10.11.254.250 -d 0.0.0.0/0 –dport 25 -j ACCEPT
sudo iptables -I smtp_out 2 -p tcp -s 10.11.254.251 -d 0.0.0.0/0 –dport 25 -j ACCEPT
sudo iptables -I smtp_out 4 -p tcp -s 0.0.0.0/0 -d 0.0.0.0/0 –dport 25 -j LOG
sudo iptables -I smtp_out 4 -p tcp -s 0.0.0.0/0 -d 0.0.0.0/0 –dport 25 -j DROP

The below statement will log all deny traffic which needs to be entered before the deny statement.

sudo iptables -I smtp_out 4 -p tcp -s 0.0.0.0/0 -d 0.0.0.0/0 –dport 25 -j LOG

Run this command to see log messages:

sudo cat /var/log/messages | grep DST=25
sudo cat /var/log/messages | grep 217.154.157.250