E-mail Without Control Panel Access by Default

[JonnyFunFun]

How can I make it so when a client adds an e-mail to one of their domains, it, by default, doesn't have "control panel access" enabled? Most of my clients don't know anything about the more advanced side of computing, and having all these accounts that can access Plesk is just a massive security risk in my mind. So how can I change this? Some source file, config file? Thanks in advance!