I've so far been unable to make the following work: I have a small cluster with a master node ( called bayes.bc.edu on the public network, and called master.cl.bc.edu on the internal 10.0.0.0 network). and a number of nodes which are purely on the private network. I want the master to receive mail and deliver locally (or use .forward and alias rules) to messages sent from the nodes to user at master, and I want it to relay non-local addresses to my campus relay host which is another machine. The relay part works ok, all mail addressed in a form that my campus relay host recognizes gets delivered. The problem is that mail to user at master.cl.bc.edu (the internal name) gets relayed to the campus relay which does not know about the host name master.cl.bc.edu because that is defined on a private DNS server for the cluster, and the campus relay rejects the message. How can I get my cluster master to not relay messages addressed to @master.cl.bc.edu? The queueing/resource manager (torque/pbs) wants to send automatic status messages to user at master.cl.bc.edu and that cannot easily be changed. Mail MTA is postfix for both master and nodes Some postfix settings on the master. myhostname = bayes.bc.edu mydomain = bc.edu myorigin = bayes.bc.edu inet_interfaces = master, localhost mynetworks = 10.0.0.0/24, 127.0.0.0/8 relayhost = mail.bc.edu and some settings on the nodes mydomain = cl.bc.edu myorigin = bayes.bc.edu inet_interfaces = localhost relayhost = [master.cl.bc.edu] Thanks for any help, Tony Schreiner