ZBilling provides a full ticket system with email alerts.
Our ticket is like a Chat Room. You can quickly add a reply to customer question, or simple assign the ticket for your co-worker.
Support Member: On change this field the owner of the ticket will be changed.
Ticket Status: If a ticket is in Open or Client Response state, this means waiting for you. So if you can´t add a reply, you can set the ticket to In Progress. This will send a email to customer that is ticket is in progress by [Support Member].