Change outgoing IP address for SMTP using iptables
Here is how you can change outgoing IP address for SMTP using iptables.
On a server, if outgoing email is being blocked by spam filters, It can sometimes get around the problem by using an IPTables rule to force the email out through a different IP address like this:
iptables -t nat -A POSTROUTING -p tcp --dport 25 -j SNAT --to-source xx.xx.xx.xx
Mostly this setting is required for gmail, outgoing email IP can be easily setup in other mail servers.
Nixtree can offer the best support to solve a several possible server management problems or requirements users can have.