Cc is an add-on for the Gmail SMTP WordPress plugin that can be used to set a Cc recipient for all outgoing email messages.
How Cc with Gmail SMTP Works
When this featured is enabled your pre-configured cc recipient will be set in the email header.

How to Enable Cc
Once you have the add-on installed, navigate to its settings (Settings > Gmail SMTP > Advanced) to set a Cc recipient.

Click “Save Changes” to update the settings.
Herbert says
Can I CC multiple users?
Noor Alam says
@Herbert, Yes you can.