ISSUENotifications are set to be delivered on customer creation. When a customer is created without a subscription, notifications are not sent. If a customer is created with a tied domain, notifications are delivered without issues.
CAUSEThis is done on purpose. There is following comment in the corresponding piece of code:
//do not notify about client creation because client cannot login without subscriptions
The notification is sent when the client's first domain is created. In other words, when the client can start to log into Control Panel.