Its giving you double replies since you are the ticket originator. It will let the agents and the ticket opener know about updates hence the double emails. Since internal notes are internal only, that is why you are getting only one email for that. You can manage notifications based on user, department, or team. By default, notifications are enabled across everything. It sounds like what you are looking for is the autoresponder. What email notifications are sent.
In that case, you login to the SCP portal as an admin, then Admin Panel, Agents, Departments. Choose the department in question and scroll down to the autoresponder settings.
For your colleague as long as they are a part of the department and team, they should get the email but the individual agent can opt out of auto responses if they have admin rights.
