Have discovered why it is that the dratted x-lite refuses to log in to my registration server despite the fact that clients written in Twisted work perfectly well. x-lite automatically searches for and finds the NAT firewall, then configures it's return address as the address of the firewall. Result is that the registration server responds to the firewall's address.

Using x-lite for debugging is a bit of a PITA. It doesn't bother to report useful error messages for connection-to-server failures, just tells you there was a failure and dumps you back to the settings dialogue. Blah.

Don't know whether to just assume we'll be fine and use simple scripts to simulate the client, or whether I'll need to get another consumer-level client that doesn't "help out" quite so much.