Within Teamwork Desk, you can enable automatic email inclusion for individual inboxes to add email addresses as CC or BCC to agent replies.
Click your profile icon in the top right corner of your Desk site, and select Settings from the dropdown menu.
In the Settings area, go to the Inboxes tab and select the inbox you wish to update.
While viewing the inbox, select Edit Inbox from the left sidebar.
You will see a section for Automatic Email Inclusion where you can add email addresses you want to be automatically included as CC or BCC on any agent replies sent from within your Teamwork Desk account.
For more information, see: Expected Behaviour for CC and BCC on an Email Thread