[lug] odd postfix message...relay attempt?

[D. Stimits]

I believe I have a postfix setup basically working correctly, but it still needs tweaking. I have relaying definitely off (thanks to earlier tips from BLUG on how to test), but I sometimes come up with this odd message in the maillog:

postfix/sendmail[2868]: fatal: parameter inet_interfaces: no local interface found for 216.239.113.148
postfix[2869]: fatal: parameter inet_interfaces: no local interface found for 216.239.113.148

Now I have absolutely no connection to 216.239.113.148, and grepping for this I don't see it anywhere, so I'm wondering if that means someone was trying to relay email? I'd like to know the nature of why it is showing up. Incidentally, the host lookup for that address is:
148.113.239.216.in-addr.arpa domain name pointer c17-ss-2-lb.cnet.com.

Google searches show a lot of hits for the line without the IP address, but none seem to offer any explanation. Can anyone enlighten me on possibilities of what is going on? At this point I've banned that IP address vi iptables, both inbound and outbound, on every port.

D. Stimits, stimits AT comcast DOT net