Date: Tue, 23 Nov 1999 02:49:32 +0200
From: Vadim Vygonets <vadik@cs.huji.ac.il>

Something Hans Matzen and I did.

# These are config file snippets for handling certain remote
# addresses as local, and making only real external addresses
# visible to users.


# Copyright (c) 1999
#	Hans Matzen <hans@tm.informatik.uni-frankfurt.de>,
#	Vadim Vygonets <vadik@vygo.net>.  All rights reserved.

#################################################################
# These are config file snippets for handling certain remote
# addresses as local, and making only real external addresses
# visible to users.
#
# First, adjust values of the following definitions, which will
# be used in configuration snippets below:

EXIM_DIR	= /var/exim
LOCAL_DOM	= home.dom
LOCAL_NET	= 192.168.0.0/16
SMART_HOST	= cc.huji.ac.il


# The scheme is to use global addresses everywhere, which is done
# by rewriting envelope sender and all headers, using a dbm file
# EXIM_DIR/in2ex, which maps internal local parts to external
# e-mail addresses using entries like:
#	user:	someone@remote.dom
#
# To do this, it good to hide hostnames in all envelope and
# header addresses first, using this rewriting rule:

*@*.LOCAL_DOM	$1@LOCAL_DOM						Eh

# Then, rewrite envelope sender and all headers to external
# addresses with this rule:

*@LOCAL_DOM	${lookup{${lc:$1}}dbm{EXIM_DIR/in2ex}{$value}fail}	Fh


# This means that envelope recipients must be somehow rewritten
# back to local addresses, which is done in one of the two
# proposed ways (you choose).
#
# One way to do it is by rewriting, using a dbm file
# EXIM_DIR/ex2in, which maps external e-mail addresses to
# internal local parts using entries like:
#	someone@remote.dom:	user
#
# This is done with the rewriting rule:
#
# *@*	${lookup{${lc:$0}}dbm{EXIM_DIR/ex2in}{$value@LOCAL_DOM}fail}	T


# The preferred way to do it is by treating certain e-mail
# addresses on remote domains as local, using route_list and self
# options to the domainlist routers, looking up e-mail addresses
# in dbm file EXIM_DIR/ex2in and throwing values away.  This is
# an example of such router.  It should probably the only router
# in the configuration.

smart_route:
   driver = domainlist
   transport = remote_smtp
   route_list = "*	${lookup{$local_part@$domain}dbm\
			  {EXIM_DIR/ex2in}{@}{SMART_HOST}}	bydns_a"
   self = local


# Then, IF local parts of some of your users are different in
# their internal and external addresses, it's nice to have the
# internal_adjust smartuser director to rewrite the address.  It
# should probably be the first director.

internal_adjust:
  driver = smartuser
  new_address = "${lookup{${lc:$local_part@$domain}}dbm{EXIM_DIR/ex2in}\
		   {$value@LOCAL_DOM}fail}"