Force outgoing mail to come from a specific IP
Add an iptables rule such as:
[code lang=”bash”]iptables -t nat -A POSTROUTING -p tcp -s ! 127.0.0.1 –dport 25 -j SNAT –to-source 220.127.116.11[/code]
This will make all outgoing mail leave over the secondary IP, 18.104.22.168, as opposed to the primary IP address of the server (the standard behavior of MTAs).