To start using VoIP, configure your VoIP hardware or software phone
to use "sip.gossiptel.com" as the domain, and "sip.gossiptel.com:5060"
as the SIP proxy. If you are behind a NAT gateway (e.g. if you
are using a 192.168.x IP address on your PC or SIP phone) then you should
use sipproxy.gossiptel.com:5060 as the outbound proxy.