I believe this indicates that your gateway address is listed within Settings>Antispam>IP Bypasses. This will cause the spam checks to ignore that IP in the received chain, and scan the previous IP in the list instead. This would move the spam checks back a step from the gateway/server address to the original client IP address. I recommend submitting a ticket on this one so we can take a closer look at your setup and provide guidance. Have a good one!
Kyle Kerst
IT Coordinator
SmarterTools Inc.
www.smartertools.com