The option mail_show_to_cc_list is installed with value "yes" but when do a manual notification and CC some people, the email recipient does not see CC list. The tech explains one possible reason for this unexpected behavior.
Release : 17.3
Component : SERVICE DESK MANAGER
When you use a custom notification method, this option can't guarantee the recipient will see the CC email list.
When do manual notification, choose the out of box email notification method.
https://techdocs.broadcom.com/us/en/ca-enterprise-software/business-management/ca-service-management/17-3/administering/administering-ca-service-desk-manager/options-manager.html