How to set "Reply all" as default in email action on case

Hi,
i need help with the following requirement:
When you click on the “email” button, only the case contact is added to the TO.
In order to add all TOs and CCs you need to click on the latest reply “reply all” link.
i want to set "Reply to all" base on the last email sent/received as default.

how can i do that?

Thanks
Dana