I defer to Len and Eric with any replies they may offer you, but in the interim I want to take a stab.
if eth0 is in /etc/hosts is eth1? What is trying to connect to it? and talk to your postfix box on that IP? Try ensuring eth1's IP is in mynetworks, etc also if you must, d/c the cable and see if the symptoms sontinue, and then you'll know if an external host or an internal process is generating the error Just some thoughts -A
