Best Practices

Creating a ticket rule that sends an email when the CC_LIST is definitely possible. The change is recorded in the HD_TICKET_CHANGE_FIELD table:

SELECT ID, FIELD_CHANGED, BEFORE_VALUE, AFTER_VALUE
FROM ORG1.HD_TICKET_CHANGE_FIELD
WHERE FIELD_CHANGED = 'CC_LIST'

The problem I see is sending that notification only to those email addresses that were added. This query illustrates the challenge:

SELECT ID, FIELD_CHANGED, BEFORE_VALUE, AFTER_VALUE, 
replace(AFTER_VALUE, BEFORE_VALUE, '') as 'New CC' 
FROM ORG1.HD_TICKET_CHANGE_FIELD
WHERE FIELD_CHANGED = 'CC_LIST'
and AFTER_VALUE like concat('%', BEFORE_VALUE, '%')

This is the simplest way I could think of to remove the values in the list before the change from the list after the change. Unfortunately, it doesn't work very well. For example, someone entered a typo in the CC list, emai, and then correct that to email@domain.com. The query result for this change is l@domain.com, which obviously isn't correct.

I would recommend sending the notification to all members in the CC list and wording the message something like "you are receiving this message because the CC list of ticket xxxx has been updated." This makes all of those aware that others are being included in ticket updates in the future.