Question Avoid creating user accounts

[auriv]

Hey ,

I use Plesk for me and a few friends. Every friend has his own account to access Plesk. When one creates a mail-account,
Plesk offers the option to create a Plesk-user for the mail account.

I do not want my friends/customers to be able to create additional accounts for Plesk by creating a new mail-account.

Is there any way to forbid creating new User/Plesk-Accounts by creating an Mail-Account in Plesk
(I mean actually the first checkbox "Use to log in to Plesk". I want it disable or invisible)

Thank you for your help, I hope you understand what I am trying to disable