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Path: utzoo!mnetor!seismo!rochester!lee
From: lee@rochester.ARPA (Lee Moore)
Newsgroups: net.mail
Subject: Re: hiding local nodes
Message-ID: <20292@rochester.ARPA>
Date: Wed, 20-Aug-86 14:01:37 EDT
Article-I.D.: rocheste.20292
Posted: Wed Aug 20 14:01:37 1986
Date-Received: Thu, 21-Aug-86 01:29:06 EDT
References: <219@munsell.UUCP>
Organization: U of Rochester, CS Dept., Rochester, NY
Lines: 33
Keywords: sendmail
Summary: yes

Yes, if you are running sendmail, then you can hide your local nodes.
We have been doing this at Rochester for years.  Basically, you hack the
sendmail.cf file so that the only machines that tack on their names
to messages are the external gateways.  Here at Rochester we have
two kinds of external gateways: uucp and arpanet.  Note that rochester.uucp
is not the same machine as rochester.arpa!  However, from the perspective
of an outside person mailing in there isn't any difference.

How is this done?  We have one sendmail.cf for all the machines.  In it is
defined which machine is the uucp gateway and which is the arpanet gateway.
If sendmail receives a message with a uucp address in it, it checks to
see if the machine that it is running on is the uucp gateway.  If it is,
then it queues the mail for uucp in the normal way.  If it is not, then it
passes the mail to the gateway machine without re-writing the header.
Once the message gets to the gateway machine, the algorithum is run again
and the right thing happens.

algorithum A:
	if mail is to uucp then
		if $HOSTNAME == $UUCP_GATEWAY_NAME then
			/* we are the uucp gateway */
			send it normally
		else
			/* we aren't the uucp gateway */
			forward the message to $UUCP_GATEWEAY_NAME
			without re-writing the header to insert
			our own name
	else if mail is arpa then
		...similar to above...
	else /* mail must be destined for this machine */
		send it locally

-=lee moore