It would be useful to add an out of the box option to create a routing rule based on the CC field of a sender email. Some users place the email address (associated with a queue) in the CC field only, and those cases auto-create but they do not get routed to the appropriate queue because the email address is not in the 'To' field. The CC field would be especially useful if you are have two queues that are sharing one case type, because then the routing rules need to be more complex in order to route the emails to the right queue.