Use the OUTPUT chain instead of the PREROUTING chain for packets originating from the local system.
Is there a way to mark packets originating on the local system?
Thanks. I tried that, but it did not seem to have any effect. The command I used was:
iptables -t mangle -A OUTPUT -j MARK --set-mark 0x0a -p tcp --dport 25
Now, when connecting from the localhost, I get:
telnet: connect to address 66.33.196.49: No route to host
I can still connect via the NAT'd systems okay.
Thanks for the assistance!
John.