# Below is an Exim 4 config file which is designed for an Exim server that
# is put in front of an Exchange 5.5 system but which verifies the valid
# addresses that are stored in Exchange via LDAP lookups against the Exchange
# server. The advantage being that I can do much more aggressive spam
# fighting, make my own set of policy decisions etc, using the flexibility of
# Exim while still supporting the Exchange system for final delivery (not my
# ideal situation but the company relies on it). In any case, I thought this
# was sufficiently useful and answers some semi-regular questions on the list,
# that it might be included in either the FAQ or the sample configs.

# From: Tabor J. Wells <twells@fsckit.net>
# Date: Wed, 21 Aug 2002 11:16:36 -0400




######################################################################
#                  Runtime configuration file for Exim               #
######################################################################


# This is a default configuration file which will operate correctly in
# uncomplicated installations. Please see the manual for a complete list
# of all the runtime configuration options that can be included in a
# configuration file. There are many more than are mentioned here. The
# manual is in the file doc/spec.txt in the Exim distribution as a plain
# ASCII file. Other formats (PostScript, Texinfo, HTML, PDF) are available
# from the Exim ftp sites. The manual is also online at the Exim web sites.


# This file is divided into several parts, all but the first of which are
# headed by a line starting with the word "begin". Only those parts that
# are required need to be present. Blank lines, and lines starting with #
# are ignored.


########### IMPORTANT ########## IMPORTANT ########### IMPORTANT ###########
#                                                                          #
# Whenever you change Exim's configuration file, you *must* remember to    #
# HUP the Exim daemon, because it will not pick up the new configuration   #
# until you do. However, any other Exim processes that are started, for    #
# example, a process started by an MUA in order to send a message, will    #
# see the new configuration as soon as it is in place.                     #
#                                                                          #
# You do not need to HUP the daemon for changes in auxiliary files that    #
# are referenced from this file. They are read every time they are used.   #
#                                                                          #
# It is usually a good idea to test a new configuration for syntactic      #
# correctness before installing it (for example, by running the command    #
# "exim -C /config/file.new -bV").                                         #
#                                                                          #
########### IMPORTANT ########## IMPORTANT ########### IMPORTANT ###########



######################################################################
#                    MAIN CONFIGURATION SETTINGS                     #
######################################################################

# Specify your host's canonical name here. This should normally be the fully
# qualified "official" name of your host. If this option is not set, the
# uname() function is called to obtain the name. In many cases this does
# the right thing and you need not set anything explicitly.

# primary_hostname =


# The next three settings create two lists of domains and one list of hosts.
# These lists are referred to later in this configuration using the syntax
# +local_domains, +relay_to_domains, and +relay_from_hosts, respectively. They
# are all colon-separated lists:

domainlist local_domains = @ : dbm;/etc/exim/db/localdomains.db
domainlist relay_to_domains = 
hostlist   relay_from_hosts = 127.0.0.1 : 192.168.1.0/24

# Most straightforward access control requirements can be obtained by
# appropriate settings of the above options. In more complicated situations, you
# may need to modify the Access Control List (ACL) which appears later in this
# file.

# The first setting specifies your local domains, for example:
#
#   domainlist local_domains = my.first.domain : my.second.domain
#
# You can use "@" to mean "the name of the local host", as in the default
# setting above. This is the name that is specified by primary_hostname,
# as specified above (or defaulted). If you do not want to do any local
# deliveries, remove the "@" from the setting above. If you want to accept mail
# addressed to your host's literal IP address, for example, mail addressed to
# "user@[192.168.23.44]", you can add "@[]" as an item in the local domains
# list. You also need to uncomment "allow_domain_literals" below. This is not
# recommended for today's Internet.

# The second setting specifies domains for which your host is an incoming relay.
# If you are not doing any relaying, you should leave the list empty. However,
# if your host is an MX backup or gateway of some kind for some domains, you
# must set relay_to_domains to match those domains. For example:
#
# domainlist relay_to_domains = *.myco.com : my.friend.org
#
# This will allow any host to relay through your host to those domains.
# See the section of the manual entitled "Control of relaying" for more
# information.

# The third setting specifies hosts that can use your host as an outgoing relay
# to any other host on the Internet. Such a setting commonly refers to a
# complete local network as well as the localhost. For example:
#
# hostlist relay_from_hosts = 127.0.0.1 : 192.168.0.0/16
#
# The "/16" is a bit mask (CIDR notation), not a number of hosts. Note that you
# have to include 127.0.0.1 if you want to allow processes on your host to send
# SMTP mail by using the loopback address. A number of MUAs use this method of
# sending mail.


# All three of these lists may contain many different kinds of item, including
# wildcarded names, regular expressions, and file lookups. See the reference
# manual for details. The lists above are used in the access control list for
# incoming messages. The name of this ACL is defined here:

acl_smtp_rcpt = acl_check_rcpt

# You should not change that setting until you understand how ACLs work.


# Specify the domain you want to be added to all unqualified addresses
# here. An unqualified address is one that does not contain an "@" character
# followed by a domain. For example, "caesar@rome.example" is a fully qualified
# address, but the string "caesar" (i.e. just a login name) is an unqualified
# email address. Unqualified addresses are accepted only from local callers by
# default. See the recipient_unqualified_hosts option if you want to permit
# unqualified addresses from remote sources. If this option is not set, the
# primary_hostname value is used for qualification.

# qualify_domain =


# If you want unqualified recipient addresses to be qualified with a different
# domain to unqualified sender addresses, specify the recipient domain here.
# If this option is not set, the qualify_domain value is used.

# qualify_recipient =


# The following line must be uncommented if you want Exim to recognize
# addresses of the form "user@[10.11.12.13]" that is, with a "domain literal"
# (an IP address) instead of a named domain. The RFCs still require this form,
# but it makes little sense to permit mail to be sent to specific hosts by
# their IP address in the modern Internet. This ancient format has been used
# by those seeking to abuse hosts by using them for unwanted relaying. If you
# really do want to support domain literals, uncomment the following line, and
# see also the "domain_literal" router below.

# allow_domain_literals


# No deliveries will ever be run under the uids of these users (a colon-
# separated list). An attempt to do so causes a panic error to be logged, and
# the delivery to be deferred. This is a paranoic safety catch. Note that the
# default setting means you cannot deliver mail addressed to root as if it
# were a normal user. This isn't usually a problem, as most sites have an alias
# for root that redirects such mail to a human administrator.

never_users = root


# The setting below causes Exim to do a reverse DNS lookup on all incoming
# IP calls, in order to get the true host name. If you feel this is too
# expensive, you can specify the networks for which a lookup is done, or
# remove the setting entirely.

host_lookup = *


# The settings below, which are actually the same as the defaults in the
# code, cause Exim to make RFC 1413 (ident) callbacks for all incoming SMTP
# calls. You can limit the hosts to which these calls are made, and/or change
# the timeout that is used. If you set the timeout to zero, all RFC 1413 calls
# are disabled. RFC 1413 calls are cheap and can provide useful information
# for tracing problem messages, but some hosts and firewalls have problems
# with them. This can result in a timeout instead of an immediate refused
# connection, leading to delays on starting up an SMTP session.

rfc1413_hosts = *
rfc1413_query_timeout = 30s


# By default, Exim expects all envelope addresses to be fully qualified, that
# is, they must contain both a local part and a domain. If you want to accept
# unqualified addresses (just a local part) from certain hosts, you can specify
# these hosts by setting one or both of
#
# sender_unqualified_hosts =
# recipient_unqualified_hosts =
#
# to control sender and recipient addresses, respectively. When this is done,
# unqualified addresses are qualified using the settings of qualify_domain
# and/or qualify_recipient (see above).


# If you want Exim to support the "percent hack" for certain domains,
# uncomment the following line and provide a list of domains. The "percent
# hack" is the feature by which mail addressed to x%y@z (where z is one of
# the domains listed) is locally rerouted to x@y and sent on. If z is not one
# of the "percent hack" domains, x%y is treated as an ordinary local part. This
# hack is rarely needed nowadays; you should not enable it unless you are sure
# that you really need it.
#
# percent_hack_domains =
#
# As well as setting this option you will also need to remove the test
# for local parts containing % in the ACL definition below.


# When Exim can neither deliver a message nor return it to sender, it "freezes"
# the delivery error message (aka "bounce message"). There are also other
# circumstances in which messages get frozen. They will stay on the queue for
# ever unless one of the following options is set.

# This option unfreezes frozen bounce messages after two days, tries
# once more to deliver them, and ignores any delivery failures.

ignore_bounce_errors_after = 2d

# This option cancels (removes) frozen messages that are older than a week.

timeout_frozen_after = 7d

# Defined LDAP default servers
ldap_default_servers = 192.168.1.101



######################################################################
#                       ACL CONFIGURATION                            #
#         Specifies access control lists for incoming SMTP mail      #
######################################################################

begin acl

# This access control list is used for every RCPT command in an incoming
# SMTP message. The tests are run in order until the address is either
# accepted or denied.

acl_check_rcpt:

  # Accept if the source is local SMTP (i.e. not over TCP/IP). We do this by
  # testing for an empty sending host field.

  accept  hosts = :

  # Deny if the local part contains @ or % or / or | or !. These are rarely
  # found in genuine local parts, but are often tried by people looking to
  # circumvent relaying restrictions.

  # Also deny if the local part starts with a dot. Empty components aren't
  # strictly legal in RFC 2822, but Exim allows them because this is common.
  # However, actually starting with a dot may cause trouble if the local part
  # is used as a file name (e.g. for a mailing list).

  deny    local_parts   = ^.*[@%!/|] : ^\\.

  # Accept mail to postmaster in any local domain, regardless of the source,
  # and without verifying the sender.

  accept  local_parts   = postmaster
          domains       = +local_domains

  # Deny unless the sender address can be verified.

  require verify        = sender

  #############################################################################
  # There are no checks on DNS "black" lists because the domains that contain
  # these lists are changing all the time. However, here are two examples of
  # how you could get Exim to perform a DNS black list lookup at this point.
  # The first one denies, while the second just warns.
  #
  # deny    message       = rejected because $sender_host_address is in a black list at $dnslist_domain\n$dnslist_text
  #         dnslists      = black.list.example
  #
  # warn    message       = X-Warning: $sender_host_address is in a black list at $dnslist_domain
  #         log_message   = found in $dnslist_domain
  #         dnslists      = black.list.example
  #############################################################################

  # Accept if the address is in a local domain, but only if the recipient can
  # be verified. Otherwise deny. The "endpass" line is the border between
  # passing on to the next ACL statement (if tests above it fail) or denying
  # access (if tests below it fail).

  accept  domains       = +local_domains
          endpass
          message       = unknown user
          verify        = recipient

  # Accept if the address is in a domain for which we are relaying, but again,
  # only if the recipient can be verified.

  accept  domains       = +relay_to_domains
          endpass
          message       = unrouteable address
          verify        = recipient

  # If control reaches this point, the domain is neither in +local_domains
  # nor in +relay_to_domains.

  # Accept if the message comes from one of the hosts for which we are an
  # outgoing relay. Recipient verification is omitted here, because in many
  # cases the clients are dumb MUAs that don't cope well with SMTP error
  # responses. If you are actually relaying out from MTAs, you should probably
  # add recipient verification here.

  accept  hosts         = +relay_from_hosts

  # Accept if the message arrived over an authenticated connection, from
  # any host. Again, these messages are usually from MUAs, so recipient
  # verification is omitted.

  accept  authenticated = *

  # Reaching the end of the ACL causes a "deny", but we might as well give
  # an explicit message.

  deny    message       = relay not permitted



######################################################################
#                      ROUTERS CONFIGURATION                         #
#               Specifies how addresses are handled                  #
######################################################################
#     THE ORDER IN WHICH THE ROUTERS ARE DEFINED IS IMPORTANT!       #
# An address is passed to each router in turn until it is accepted.  #
######################################################################

begin routers

# This router routes to remote hosts over SMTP by explicit IP address,
# when an email address is given in "domain literal" form, for example,
# <user@[192.168.35.64]>. The RFCs require this facility. However, it is
# little-known these days, and has been exploited by evil people seeking
# to abuse SMTP relays. Consequently it is commented out in the default
# configuration. If you uncomment this router, you also need to uncomment
# allow_domain_literals above, so that Exim can recognize the syntax of
# domain literal addresses.

# domain_literal:
#   driver = ipliteral
#   domains = ! +local_domains
#   transport = remote_smtp


# This router routes addresses that are not in local domains by doing a DNS
# lookup on the domain name. Any domain that resolves to 0.0.0.0 or to a
# loopback interface address (127.0.0.0/8) is treated as if it had no DNS
# entry. Note that 0.0.0.0 is the same as 0.0.0.0/32, which is commonly treated
# as the local host inside the network stack. It is not 0.0.0.0/0, the default
# route. If the DNS lookup fails, no further routers are tried because of
# the no_more setting, and consequently the address is unrouteable.

dnslookup:
  driver = dnslookup
  domains = ! +local_domains
  transport = remote_smtp
  ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8 : 10.0.0.0/8 : 172.16.0.0/12
  no_more


# The remaining routers handle addresses in the local domain(s).


# This router handles aliasing using a traditional /etc/aliases file.
#
##### NB  You must ensure that /etc/aliases exists. It used to be the case
##### NB  that every Unix had that file, because it was the Sendmail default.
##### NB  These days, there are systems that don't have it. Your aliases
##### NB  file should at least contain an alias for "postmaster".
#
# If any of your aliases expand to pipes or files, you will need to set
# up a user and a group for these deliveries to run under. You can do
# this by uncommenting the "user" option below (changing the user name
# as appropriate) and adding a "group" option if necessary. Alternatively, you
# can specify "user" on the transports that are used. Note that the transports
# listed below are the same as are used for .forward files; you might want
# to set up different ones for pipe and file deliveries from aliases.

system_aliases:
  driver = redirect
  allow_fail
  allow_defer
  data = ${lookup{$local_part}lsearch{/etc/exim/txt/aliases.txt}}
# user = exim
  file_transport = address_file
  pipe_transport = address_pipe

# This router matches local user mailboxes.
# Domains set to $primary_hostname so that I can route stuff locally as need
# be but prevent user@mylocaldomain.com from delivering locally when 'user'
# also matches the Exchange lookup below.

localuser:
  driver = accept
  check_local_user
  domains = $primary_hostname
  transport = local_delivery
  no_more

# Routers for lookups in LDAP on Exchange if they exist there then punt

# First if it exists as a otherMailbox=smtp$user@example.com (Exchange's
# format for aliases then substitute the canonical email address for this user
# as defined by mail=

exchangeothermailboxlookup:
  driver = redirect
  data = ${lookup ldap {ldap:///?mail?sub?(otherMailbox=smtp\$${quote_ldap:$local_part}@${quote_ldap:$domain})}}
  domains = dbm;/etc/exim/db/localdomains.db
  verify_recipient

# This lookup verifies the mail=user@example.com format and if it exists
# Pass to the the manualroute router which is used to punt to the internal
# Exchange server as defined by domain.

exchangemaillookup:
  driver = redirect
  data = ${lookup ldap {ldap:///?mail?sub?(mail=${quote_ldap:$local_part}@${quote_ldap:$domain})}}
  domains = dbm;/etc/exim/db/localdomains.db
  verify_recipient
  self = pass
  pass_router = exchangeroute
  no_more

# localdomains.db contain entries that look like:
# example.com: 192.168.1.101
# example.net: 192.168.1.102
# etc.

exchangeroute:
  driver = manualroute
  transport = remote_smtp
  route_data = ${lookup{$domain}dbm{/etc/exim/db/localdomains.db}}

######################################################################
#                      TRANSPORTS CONFIGURATION                      #
######################################################################
#                       ORDER DOES NOT MATTER                        #
#     Only one appropriate transport is called for each delivery.    #
######################################################################

# A transport is used only when referenced from a router that successfully
# handles an address.

begin transports


# This transport is used for delivering messages over SMTP connections.

remote_smtp:
  driver = smtp


# This transport is used for local delivery to user mailboxes in traditional
# BSD mailbox format. By default it will be run under the uid and gid of the
# local user, and requires the sticky bit to be set on the /var/mail directory.
# Some systems use the alternative approach of running mail deliveries under a
# particular group instead of using the sticky bit. The commented options below
# show how this can be done.

local_delivery:
  driver = appendfile
  file = /var/mail/$local_part
  delivery_date_add
  envelope_to_add
  return_path_add
# group = mail
# mode = 0660


# This transport is used for handling pipe deliveries generated by alias or
# .forward files. If the pipe generates any standard output, it is returned
# to the sender of the message as a delivery error. Set return_fail_output
# instead of return_output if you want this to happen only when the pipe fails
# to complete normally. You can set different transports for aliases and
# forwards if you want to - see the references to address_pipe in the routers
# section above.

address_pipe:
  driver = pipe
  return_output


# This transport is used for handling deliveries directly to files that are
# generated by aliasing or forwarding.

address_file:
  driver = appendfile
  delivery_date_add
  envelope_to_add
  return_path_add


# This transport is used for handling autoreplies generated by the filtering
# option of the userforward router.

address_reply:
  driver = autoreply



######################################################################
#                      RETRY CONFIGURATION                           #
######################################################################

begin retry

# This single retry rule applies to all domains and all errors. It specifies
# retries every 15 minutes for 2 hours, then increasing retry intervals,
# starting at 1 hour and increasing each time by a factor of 1.5, up to 16
# hours, then retries every 6 hours until 4 days have passed since the first
# failed delivery.

# Domain               Error       Retries
# ------               -----       -------

*                      *           F,2h,15m; G,16h,1h,1.5; F,4d,6h



######################################################################
#                      REWRITE CONFIGURATION                         #
######################################################################

# There are no rewriting specifications in this default configuration file.

begin rewrite



######################################################################
#                   AUTHENTICATION CONFIGURATION                     #
######################################################################

# There are no authenticator specifications in this default configuration file.

begin authenticators


# End of Exim configuration file
