What the gentleman has is a very common configuration on corporate intranets... firewall.imagineering is a FQDN -- but only inside his LAN. .imagineering is the top-level domain they use within their LAN, and the internal mail servers use names with that domain. Those names cannot be expected to be able to be resolved on the open Internet, as they only work inside his LAN. That doesn't change the fact that servers inside his LAN act as mail relays before the mail gets to him. However, from previous experience, I believe spamcop's parser IS smart enough to recognize IP addresses that are in a private address space and write off that Received header as an internal mail server if the IP is displayed and in a private range. The headers your server is generating are putting the IP address of the original sender in that spot instead of the IP address of the server it received the mail from. That's the part that's throwing off the parser.