postinst is in spamass-milter 0.3.1-10build1.
This file is a maintainer script. It is executed when installing (*inst) or removing (*rm) the package.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 | #!/bin/sh
set -e
case "$1" in
    configure)
        # Create the spamassmilter user
	if [ -x /usr/sbin/adduser ]; then
	    if ! id -u spamass-milter >/dev/null 2>&1; then
		adduser --system --home /var/lib/spamass-milter spamass-milter;
	    fi;
	fi;
	# Attempt to remove /var/run/spamass if it exists
	# If we're upgrading from -4 or earlier, we want to remove the
	# pidfile if spamass.milter isn't running, and then remove
	# /var/run/spamass
	if dpkg --compare-versions "$2" 'lt' '0.3.1-5'; then
	    if [ -f /var/run/spamass/spamass.pid ] && ! kill -0 "$(cat  /var/run/spamass/spamass.pid)"; then
		rm -f /var/run/spamass/spamass.pid;
	    fi;
	    if [ -d /var/run/spamass ]; then
		rmdir --ignore-fail-on-non-empty /var/run/spamass ;
	    fi;
	fi;
	;;
    *)
	# do nothing
	;;
esac
    
### Automatically added by dh_installinit
if [ -x "/etc/init.d/spamass-milter" ]; then
	if [ ! -e "/etc/init/spamass-milter.conf" ]; then
		update-rc.d spamass-milter defaults >/dev/null
	fi
	invoke-rc.d spamass-milter start || exit $?
fi
# End automatically added section
##
exit 0;
 |