There is one caveat where Unity does not use the last port available for MWI notification, and that is when you are integrating with an Avaya G3 using the Calista PBX Link and you are not using analog lamping. In this case, by default Unity uses port memory. With port memory on, Unity will attempt to use the highest numbered available port to light the lamp, and when it is time to turn off the lamp, instead of using the highest numbered available port to turn off the lamp, it will use the port that it orignally used to turn on the lamp.
I should note that by default even the Unity switch file that is set up for analog lamping uses port memory. This can be turned off, but it requires you to progam the ports used for lamping as VMI ports on the switch, and remove the from the VM hunt group. If a port is programmed as a VMI port on the switch, any other port programmed as a VMI port can turn off the lamp.
Port memory was designed for switches that require the same port that lit a lamp to be the same one to turn it off.
