This option allows remote systems to initiate new connections in order to do file transfers through Messenger. This option will open the specified port range on the firewalled system. It defaults to ports 6891 through 6900. I'm not sure if Messenger can be configured to use different ports like ICQ and AIM, but if it can, the defaults can be modified. The Messenger protocol client must be running on the firewalled system. Use the advanced port forwarding option if you wish to support port forwarding to an internal system.