Steps to Reproduce
Navigate to Incident > Open and open an active incident from the incident table.
Click … at the top of the incident and click Email.
Provide a valid email address (for example, your own) for the To and CC fields, type something into the body, and then click Send.
Note that in UI16, the CC field does not show in the activity formatter.
Switch to UI11 (navpage.do?sysparm_device=desktop) and open the same incident.
Note that the CC field is displayed in the activity formatter.
Use UI15 instead of UI16. If you are able to upgrade, review the Fixed In field to determine the versions that have a permanent fix.
Related Problem: PRB667491