How To Set Up Mail-out-only System ?

[Nick Boyce <nick@glimmer.demon.co.uk>]

Sorry if this is a dumb question ...

I've just set up a "secure" (you know .. more than usual) Debian system, 
and want to arrange things so that it can send mail out when necessary 
(in case anything happens that it thinks I should know about) but is 
*not* constantly listening for incoming mail.

Is there a best way of doing this ?

The default Exim MTA is installed, and I've commented out the SMTP line 
from inetd.conf, but there is a /etc/init.d/exim startup script that 
comes with the Exim package, that has this :

   # Exit if exim runs from /etc/inetd.conf
   if [ -f /etc/inetd.conf ] && grep -q "^ *smtp" /etc/inetd.conf; then
       exit 0
   fi
   [...]
   case "$1" in
     start)
       echo -n "Starting MTA: "
       start-stop-daemon --start --pidfile /var/run/exim/exim.pid \
                               --exec $DAEMON -- -bd -q30m

So one way or the other, Exim gets to listen.

In exim.conf, there is 
   # This will cause it to accept mail only from the local interface
   #local_interfaces = 127.0.0.1
so I could set that option.  Would that stop Exim from binding to the 
ethernet interface ?

Should I just remove the S20exim symlink from rc?.d ?
That seems a bit of a kludge.  If this was NetBSD, I'd set something 
like "exim=no" in somewhere like rc.conf ... is there a Debian 
equivalent to that ?

TIA for any advice.
Nick Boyce
Bristol, UK