Initial Setting: User-registered Domain Settings
Sets the domain of the email address which the user can register anew.
From the hamburger menu on the Global Navigation Bar, click on [Settings].
Open the setting screen by clicking "User-specified Domain Settings," and then click "Add User-registered Domains."
Enter the domain of the newly registered email address to "Authorized Domains" and then click "Add". By unchecking "Enable", registration will become invalid.
Enter Domain using the correct format
When word strings that are not domains are entered to "Authorized Domains," an error message will show up.