I have recently moved all my data and settings to a new Mac, including my Mailboxes and Apple Mail.app settings. Now I want to keep my old MacBook as a secondary device and keep the user profile as well, but I want to make absolutely sure that the old Mail settings do not kick in and retrieve some mail from the mail servers. I don't want to use Mail on this system any more. How do I reliably kill all data and settings of Mail.app?
After cutting all network connections, I started Mail and was greeted with the default Welcome wizard - so I assume that this was the solution.