Hi @M
Welcome to our forum!
Based on my research, it is not yet supported to add an automatic CC rule directly in New Outlook. I am afraid that you need to switch back to the legacy Outlook to continue to use this feature.
However, there is a workaround that you may Bcc yourself each time you send an email, and then forward the email received from yourself to your colleague, as shown in the image:
In addition, i have found a post in feedback collection website, and you could vote for it. Please kindly understand that many functions are not designed at present. Many features of our current products are designed and upgraded based on customers’ feedback. You can also make suggestions on that website and hope Microsoft will notice this in the future.
Hope it helps!
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our [documentation] to enable e-mail notifications if you want to receive the related email notification for this thread.