Hi, not sure if this is the right forum (maybe the ISA boards) but is there any documentation regarding ISA and the sender ID? I have read the docs on sp2 and entered the IP of the Exchange server as an internal server but am not positive about entering the IP of the ISA server it is behind as an internal server that handles the email? does it do this transparently or does it need to be entered? Should it be the internal or external address that you would enter? Any ideas? Thanks TD