[pptp-server] Non-local connection attempts fail

[Christopher Biow]

I have PoPToP 1.0.0 server set up and working on our RedHat 6.0 server, at
mail.ezmort.com. VPN connections to it work fine from both local subnets;
either our Internet block  209.183.239.0/28, or the masqueraded local
10.0.0.0/24. However, external connections from outside our router (a
Flowpoint 144 IDSL at 209.183.239.1) fail after about 30 seconds, with
Error 650 (occasionally 629). I *can* use a telnet client to connect from
outside to mail.ezmort.com:1723, though of course it drops the connection
after two bytes are actually sent.