In the WHM, go to : Exim Configuration Editor, Advanced Editor
In the Router Section Add the 4 lines (Look at the screen shot)
static_route:
driver = manualroute
transport = remote_smtp
route_data = ${lookup{$domain}lsearch{/etc/staticroutes}}
After go into SSH and edit the following file :
nano /etc/staticroutes
The structure will be : (domainname: ip)
domain.com: 222.222.222.222
To ensure Exim will accept the domain to relay edit the following file :
nano /etc/secondarymx
The structure will be : (domainname)
domain.com
On the new Release of CPANEL, the screen shot is :