[otrs] Sending escalation more than once

Hello, I would like to send e-mail notification. My scenario is like this: First response time : 10mins Update time : 15 minutes Solution time : 40 minutes If no response is sent, escalation e-mail should be sent as soon as first response time exceeds. In this scenario, 10mins later, an e-mail should be sent. Noone replied or updated and time passed 16 mins, that means update time exceeded. Another escalation massage should be sent. After 41 minutes, noone did nothing, new escalation message should be sent. In my system, only one escalation message is sent. How can I manage to send e-mail for each escalation. Regards, Aysel Pamuk