Go through the following steps in order to Change SMTP Server IP (Exim IP) on WHM Server
remote_smtp: driver = smtp
interface = ${if exists {/etc/mailips}{${lookup{$sender_address_domain}lsearch{/etc/mailips}{$value}{}}}{}}
helo_data = ${if exists {/etc/mailhelo}{${lookup{$sender_address_domain}lsearch{/etc/mailhelo}{$value}{$primary_hostname}}}{$primary_ho stname}}
remote_smtp:
driver = smtp
interface = 12.14.12.14 # Change to your server IP address.
If there is an Exim update when you upgrade your cPanel server you will need to re-enter the interface again.