hey ppl,
i new to ser and i am struck at a point. I have 3 local machines 
and i have set them up as shown

dialer  ----->   ser ---------> pstn gateway

when i register to ser i use user at IPaddress:Port and then simply
dial a pstn number in the script i am simply forwarding it to a 
pstn gateway ....
Now my question is when SER forwards the request to the PSTN gateway
it adds a new via header in which it uses IPaddress:Port whereas i want
ser to use the domain that has been specified on the ser machine using
export SIP_DOMAIN = "test domain" command
First of all can i do that if yes please guide me how to do that ...
and how do i make ser use example.domain ... is there any other way ??? 
I am using the hello world cfg file .... with no db / media proxy support.

please correct me and help me  thanks in advance 
Zeeshan