Forwarding the ports won't work unless you change the UDP port closing time to be longer than the registration interval (which is one hour - 3600 seconds). UDP port on most routers expire in 300 seconds so if you registered and try to call yourself after 5 minutes, chance are ExpressTalk won't ring. I think at least my version of ExpressTalk (v4.03) does NOT send "Keep Alive" packet to keep the UDP port open; hence, this problem. I haven't figure out a way to workaround this shortcoming of ExpressTalk yet short of changing my UDP closing time to 3600 (which I try to avoid doing).