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

This is an Exim filter snippet to change locally-generated 
Message-Id: and Resent-Message-Id: headers to world-unique values.


# Exim filter

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

#################################################################
# Change locally-generated Message-Id: and Resent-Message-Id:
# headers to world-unique values.

# Notes:
# Change every occurence of "home.dom" to your home domain.
# Change every occurence of "uniqie.remote.dom" to some unique value.

# Unique values, as Vadik explained in his message to exim-users,
# can be chosen in different ways:

### The ideal way is to choose "hostnames" in existing domains whose
### admins you know, and you will be sure that no hostname ending
### with ".nonexistant.friendly.dom" will ever appear on this planet,
### not even on someone else's message IDs.

### Another ideas include putting after your hostname things like:
### .972.2.6412694.phone
### .29.32.columbia.street.jerusalem.96583.israel.addr
### .1122.3576.3847.1446.visa.01.2002.expiration.date.vadim.vygonets.name.credit.card

# This snippet provides to schemes to do such rewriting.  The
# first scheme is to have mapping from local hostnames to unique
# "Message-Id domains".  The second scheme is to use one unique
# "Message-Id domain", inserting the original "domain" into the
# "local-part" of the new Message-Id header.

# Precaution
headers remove "X-Vygo-Net-Temporary-Message-Id"

# Change Message-Id:
if "${if def:h_Message-Id: {yes}}" is yes and 
    ${lc:${domain:$h_Message-Id:}} is    "home.dom" or
    ${lc:${domain:$h_Message-Id:}} ends ".home.dom" then
# This is if you want to have a file mapping each hostname to a unique
# Message-Id domain part, or, if it fails, preserves the original domain part:
#	headers add "X-Vygo-Net-Temporary-Message-Id: <${local_part:$h_Message-Id:}@${lookup{${domain:$h_Message-Id:}}lsearch{/var/exim/msgid-hosts}{$value}{${domain:$h_Message-Id:}}}>\n"
# This rewrites Message-Id as <local_part.domain@unique.domain>:
	headers add "X-Vygo-Net-Temporary-Message-Id: <${local_part:$h_Message-Id:}.${domain:$h_Message-Id:}@unique.remote.dom>\n"
	headers remove "Message-Id"
	headers add "Message-Id: $h_X-Vygo-Net-Temporary-Message-Id:"
	headers remove "X-Vygo-Net-Temporary-Message-Id"
endif

# Change Resent-Message-Id:
if "${if def:h_Resent-Message-Id: {yes}}" is yes and 
    ${lc:${domain:$h_Resent-Message-Id:}} is    "home.dom" or
    ${lc:${domain:$h_Resent-Message-Id:}} ends ".home.dom" then
# This is if you want to have a file mapping each hostname to a unique
# Message-Id domain part, or, if it fails, preserves the original domain part:
#	headers add "X-Vygo-Net-Temporary-Message-Id: <${local_part:$h_Resent-Message-Id:}@${lookup{${domain:$h_Resent-Message-Id:}}lsearch{/var/exim/msgid-hosts}{$value}{${domain:$h_Resent-Message-Id:}}}>\n"
# This rewrites Message-Id as <local_part.domain@unique.domain>:
	headers add "X-Vygo-Net-Temporary-Message-Id: <${local_part:$h_Resent-Message-Id:}.${domain:$h_Resent-Message-Id:}@unique.remote.dom>\n"
	headers remove "Resent-Message-Id"
	headers add "Resent-Message-Id: $h_X-Vygo-Net-Temporary-Message-Id:"
	headers remove "X-Vygo-Net-Temporary-Message-Id"
endif