Tricky. Do you mean "other SIP domain that you have no control over whatsoever"?? If so, you're probably stuck doing some basic src_ip matching if (src_ip==ip.address.of.other.domain) { rewritehostport("ip.address.that.i.want.it.to.go.to"); if (!t_relay()) { blah; blah; blah; }; }; if, you do have some relation with that domain, then you can just add a proxy_authorize. i.e. if (src_ip==ip.address.of.other.domain) { rewritehostport("ip.address.that.i.want.it.to.go.to"); if (!(proxy_athorize("my.domain", "subscriber")) { if (method!="ACK" & method!="BYE") { proxy_challenge("aptela.com", "0"); break; }; }; if (!t_relay()) { blah; blah; blah; }; }; Java Rockx wrote: