[Serusers] SER on masqueraded/NAT connection

I have a Linux box at home acting as a masquerading/NAT gateway for a few Windows PCs, and have installed SER on there in order to use MS Messenger to talk to people outside. SER appears to be working in that I can get Messenger up on two PCs, connect to SER and set up a voice connection between the two PCs. However, I cannot connect to people offsite. Relevant IPChains entries are target prot opt source destination ports ACCEPT udp ----l- anywhere anywhere any -> 5060 ACCEPT udp ------ anywhere anywhere any -> 7070:7080 I have made no changes to the default SIP configuration; it is working as installed by the rpm package ser-0.8.10-1.i386.rpm. A browse through the mailing list archive and through the admin guide doesn't show anything obvious. No errors are reported to /etc/messages or /etc/syslog and serctl moni does not show anything that looks relevant. Does anyone have any suggestions? -- Dr. Craig Graham, Software Engineer Advanced Analysis and Integration Limited, UK. http://www.aail.co.uk/