We could not receive mail from the Hormel (Redhat List) server. We were receiving the rest of our mail without a problem. Our server has three internal IPs on two interfaces; eth0, eth0:1, eth1. The router sent (NAT'd) services to the appropriate IP. Anything that wasn't NAT'd was sent to eth0:1 where the packets were logged and then rejected by IPTables. This was done exclusively through FILTER/INPUT. There were NO - zero - other rules in the firewall. Now here's the weird part. Packets from Hormel - and ONLY Hormel - were mangled. They showed up as UDP instead of TCP and then were assigned to an array of ports - none being 25. As soon as I stopped IPTables, the problem went away which means that there is no problem on the router end. Moreover, how could this possibly pertain ONLY to the Hormel server. Does anyone have any ideas?
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