You can change exim outbound mail ip for a domain from cPanel using the below mentioned method.

Edit the file “mailips” from the server. Use the command below for that,

vi /etc/mailips

This file will assign the ip’s from which each domain should send mail. You need to edit this file and add the following line to it, in which the domain name and IP address is needed to specified.

Here is an example for the entry you need to added to the file,

iserversupport.com: 192.168.XXX.XXX

You need to add the domain you need to assign the mail IP and the IP address in the above mentioned format.

For changing the mailip for all the domains just add the line line below to the file,

*:  192.168.XXX.XXX

Then restart the exim. After that the mails from the mentioned domain will go through the IP assigned to it.