[SR-Users] Kamailio as simple SIP proxy between client and SIP server.

This is my current setup, which works: SIP client <-> SIP server. As I've currently moved to another country I would like to be able to do the following setup: SIP client <-> Kamailio SIP proxy <-> SIP server. As the SIP server only accept packets from specific IP's. Is it possible? I've managed to setup a simple Kamailio installation on my server, which does have a valid IP for the SIP server. With the Kamailio installation I've also enabled NAT with RTPProxy. My problem is now, that the Kamailio installation doesn't work as a simple proxy, but actually takes registrations etc. and acts as a "full-blown" SIP server. It should only take SIP messages and transfer them between clients and server. Any ideas?