OSTicket will open a new ticket if the Client does not reply to the original message, or of course if Customer Services did not reply to them Via OSTicket.
For it to work properly
1. Client sends in email - OS Ticket creates a new ticket.
2. Customer services reply via SCP
3. Client replies to the message - this message will be appended to the original ticket.
For the new message to be appended it must be from the same e-mail address as the orginal and have the ticket number in the Subject line.