In cPanel enviroment, you can edit the outgoing IP by edit /etc/mailips. This file controls the IP address from which each domain should send mail.
It can be configure this file in the following way:
Example 1 : all kc.com outgoing mail IP is 192.168.0.2
Example 2 : sub.kc.com outgoing mail IP is 192.168.0.3
Example 3 : All domain in this server will use outgoing IP 192.168.0.1
Note: after done the setting, make the file /etc/mailips immutable. This to ensure the file is not reseted after service restart.
chattr +i /etc/mailips
Last step, restart the service