I have a client that has just changed over from a desktop to a laptop. On his desktop, I had setup a dummy POP account in Outlook. This was so he could send emails from his other email address without there being "sent on behalf of...." on the email. The dummy POP account used the Exchange server on SBS2003 as the SMTP server to send email. I had the server accept relays from the static IP address of his desktop so it wasn't an open relay.
Now that he has a laptop and uses wireless, ethernet, RPC - HTTP, how do I set the server to accept email relay for just him as his IP address will be constantly changing.