CCing non registered users/unverified email

Hi !

We have set up a restricted access to our Zendesk instance with some domains listed in the allow list and all other users suspended with * in the blocked list.

What is the expected behavior when a user is added as a CC to a ticket when

1. CC’s email is in the allow list but is not registered or already registered but the email is not verified yet.
2. CC’s email is not in the allow list.

It looks like in either case the CC will be added as a new user, but I want to be sure there will be no problem  at least for the 1st case.

I tested the case 2 with a requester adding a CC from the request form - although having been added as a new user and received the agent's reply as CC,  the CC was removed from the ticket at some point (after the requester replied all) so I'm a bit confused.