You can change the maximum number of emails allowed for a particular domain to a different number than the system default using the file (Other than WHM settings)
/var/cpanel/maxemails
Just add an entry like “domain.com = 100″ . Now 100 is the maximum email per hour limit for domain.com.
But please make sure that you have executed the following script after updating the file /var/cpanel/maxemails.
#/scripts/build_maxemails_config