You have to be carefull with Mitel. First of all you have to make sure that only one and the same port is turning MW light ON & OFF. Secondly make sure that the port not in Hunting group and move all other ports to COS that has Message Send future Disable. Sometime with Repartee you have to adjust length off ring because Mitel won't respond on short ring. That is why with the test set you have no problem but with the port you do, even you see port is sending the right string.