[Serusers] SER Public address prob

Hi, Just wondering if anyone can shed light on the following: I have ser installed on a machine with address 172.x.x.x. I want clients to register with a public address 84.x.x.x. I then have natting in place which maps it to a 192.x.x.x address and a router forwards it to the 172.x.x.x address if its a sip message (port forwarding). However I have been trying to register using a windows messenger sip address aisling(a)84.x.x.x and its not working...... Shoulds a scenario like this work? Basically the idea is that anybody on any network can register with this public address (84.x.x.x) which will be natted to 192.x.x.x and forwarded at a router to 172.x.x.x if its a sip message. Thanks! Aisling. -------------------Legal Disclaimer--------------------------------------- The above electronic mail transmission is confidential and intended only for the person to whom it is addressed. Its contents may be protected by legal and/or professional privilege. Should it be received by you in error please contact the sender at the above quoted email address. Any unauthorised form of reproduction of this message is strictly prohibited. The Institute does not guarantee the security of any information electronically transmitted and is not liable if the information contained in this communication is not a proper and complete record of the message as transmitted by the sender nor for any delay in its receipt. ----------------------------------------------------------------------------------------