global limit space
For now, you can define an max quota mailbox, number of maibox and max quota hosting in panel. For exemple, if you define, 100M of hdd quota, 100M of mailbox quota and 10 mailbox, the global limit is about 1,1G. We love the idea to put an global space (for exemple 500M) and an page with selector to assign an part max of this space to all component (for exemple, 100M for HDD, 50M for mailbox1, 350M for mailbox2) and have no excess space posible in an suscription (something like this for each component : https://jqueryui.com/slider/)...
Unfortunately, we have to close your request, because over the years it has not become quite popular for further implementation.