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


# This is a configuration file for an efficient MX receiver. We store
# all incoming mail in Maildirs, and it's all owned by a single user
# (exim) so that our clients do not need entries in /etc/passwd.

# The files we use are:
#    /usr/exim/vdomains.db
#       List of all domains which we receive mail for. These can
#       be individual (example.com) or wildcard (*.example.com)
#    /usr/exim/valiases.db
#       List of E-mail addresses and destinations we deliver to.
#       See the description below under the 'valiases' director.
#    /usr/exim/mquota.db
#       Quota for each maildir, if other than the default. Entries
#       are of the form:
#           /path/to/maildir/    25000000

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


# Macro to define the default quota (in bytes) for accounts not listed in
# the quota file.

DEFQUOTA = 10000000


# For efficiency, local domains are held in a CDB file. We can have
# many thousands of virtual domains hosted on this box.
# partial matching is allowed (e.g. an entry in the CDB file of
# *.your.domain will match anything.your.domain)

# @ (the fully-qualified domain name of this host) is just
# so we can accept postmaster@this.host

local_domains = partial2-dbm;/usr/exim/vdomains.db : localhost : @


# As an incoming MX receiver. we do not allow relaying, either from
# clients or as a backup MX to anywhere else.

host_accept_relay =
relay_domains =


# 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 = *

# Disallow recipients of the form user@[x.x.x.x]

forbid_domain_literals

# This line makes incoming recipient addresses be verified during the
# SMTP dialogue. Unknown recipients are then rejected at this stage,
# and the generation of the failure message is the job of the sending host.
# (In particular, we don't have to bounce spam to unknown addresses)

receiver_verify

# Verify incoming sender addresses (return-paths) during the SMTP dialogue.
# Verification can normally only check that the domain exists.

sender_verify


# You might want to reject mail from senders who are listed in realtime
# blackhole lists. The advantage is some reduction in received spam;
# the cost is that it applies to your entire userbase, and there will
# be false positives (i.e. genuine mail which is bounced just because
# the sending machine is RBL listed). See http://www.mail-abuse.org/

# rbl_domains = blackholes.mail-abuse.org:dialups.mail-abuse.org


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

ignore_errmsg_errors_after = 2d

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

timeout_frozen_after = 7d

# For a busy server, increase the maximum number of incoming SMTP sessions
# from the default of 20

smtp_accept_max = 300

# By default, if more than 10 messages are receiving in one SMTP session,
# they are queued rather than being delivered immediately. This is supposed
# to help when our server comes back after a long period of downtime and
# there is a lot of mail waiting for us on other systems. The limit is
# a bit low for a big mail server.

smtp_accept_queue_per_connection = 50

# It's safe to accept 8BITMIME, since all our received mail is delivered
# locally rather than being relayed (so we shouldn't need to convert it
# to 7BIT when talking to another host)

accept_8bitmime

# Security settings. The first two should not be required if we compiled
# exim with the right EXIM_UID and EXIM_GID settings.
# Setting 'security = unprivileged' forces Exim to change to the exim
# user/group almost immediately after starting. See section 55.2 in
# the documentation.

# exim_user = exim
# exim_group = exim
never_users = root
security = unprivileged

# If you want mail logs to go to a central syslog server, set this and
# put "mail.info     @syslog.host" in /etc/syslog.conf

# log_file_path = syslog

end



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

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


# This transport is used for delivering messages over SMTP connections.
# In our case it is only used for returning bounces to sender, or
# where the database specifies that the user wants their mail forwarded
# elsewhere.

remote_smtp:
  driver = smtp


# Delivery to Maildir file as user 'exim'

# Version 1: using exim's built-in Maildir support. This is fine but
# does not handle quotas well when there are thousands of files in a
# mailbox.

maildir_internal:
  driver = appendfile
  maildir_format

  user = exim
  group = exim

  no_delivery_date_add
  envelope_to_add
  return_path_add
  # with Maildir, we do not add a "From " line, and do not need to
  # convert "From " to ">From "
  prefix =
  suffix =
  check_string =
  escape_string =

  # Record the size of each file in the filename as ,S=xxx
  # This means we only have to do a readdir(), we don't have to
  # stat() each file individually to find its size.
  maildir_tag = ,S=$message_size
  quota_size_regex = ,S=(\d+)

  # Quota handling
  quota = ${lookup{$address_file}dbm{/usr/exim/mquota.db}{$value}{DEFQUOTA}}
  quota_warn_threshold = 90%
  quota_warn_message = "\
  	To: $local_part@$domain\n\
  	Subject: Your mailbox\n\n\
  	This message is automatically created by mail delivery software.\n\n\
  	The size of your mailbox has exceeded a warning threshold that is\n\
  	set by the system administrator.\n"


# Version 2: using the 'deliverquota' command provided as part of
# courier, which returns 0 in the case of successful delivery or
# 77 (EX_NOPERM) if it was over quota.
# This is more efficient, as it implements Maildir++ which calculates
# quotas using the 'maildirsize' file. See maildir/README.maildirquota.txt
# in the courier distribution.
# The '-c' option to deliverquota makes it create Maildirs automatically
# for new accounts, and "-w 90" delivers a warning message when the mailbox
# gets over 90% full. Create /usr/courier-imap/etc/quotawarnmsg with the
# full message (headers, blank line, text)

# Note: the S on the end of the quotas is required by Courier, for which
# 10000000S means "10000000 bytes", but 1000C means "1000 messages"

maildir_courier:
  driver = pipe
  command = /usr/courier-imap/libexec/deliverquota -c -w 90 "${address_file}" "${lookup{$address_file}dbm{/usr/exim/mquota.db}{$value}{DEFQUOTA}}S"

  return_fail_output

  user = exim
  group = exim

  no_delivery_date_add
  envelope_to_add
  return_path_add
  # with Maildir, we do not add a "From " line, and do not need to
  # convert "From " to ">From "
  prefix =
  suffix =
  check_string =
  escape_string =


end



######################################################################
#                      DIRECTORS CONFIGURATION                       #
#             Specifies how local addresses are handled              #
######################################################################
#                          ORDER DOES MATTER                         #
#   A local address is passed to each in turn until it is accepted.  #
######################################################################

# Local addresses are those with a domain that matches some item in the
# "local_domains" setting above, or those which are passed back from the
# routers because of a "self=local" setting (not used in this configuration).

# Remember that local_domains includes all our virtual domains.
# First, ONLY for mail addressed directly to this host, look up local_part
# in /etc/aliases for somewhere to forward it (for postmaster, abuse etc)

system_aliases:
  # This director used ONLY for mail addressed directly to this server
  domains = localhost : @

  driver = aliasfile
  file = /etc/mail/aliases
  search_type = lsearch


# For all other domains, we look up in valiases.db for entries
# like this:
#
#   user@example.com: /path/to/maildir/  # match exactly this address
#   *@example.com:    /path/to/maildir/  # match <anything>@example.com
#   user@example.com: :fail:                     # bounce
#   user@example.com: :fail:This user has left   # send a specific bounce msg
#   user@example.com: :blackhole:                # discard silently
#   user@example.com: user2@elsewhere.com        # forward externally
#
# The search type "dbm@*" means "look up the key in the dbm database; if no
# entry is found then replace everything to the left of @ with * and look
# it up again". Hence an exact match of user@domain will be used in
# preference to a wildcard *@domain, if both exist.

# SECURITY NOTE: users must NOT be allowed to edit their own entries in
# this database, otherwise /they/could/overwrite/ files on your machine!
# If you want user-controlled forwarding then set up a separate director
# in front of this one. Set forbid_file, forbid_pipe, forbid_include and
# forbid_special so that they can only forward to other E-mail addresses.

valiases:
  driver = aliasfile
  search_type = dbm*@
  file = /usr/exim/valiases.db
  include_domain
  qualify_preserve_domain

  # For alias entries /which/look/like/this/, we deliver directly to a
  # Maildir at this location. Hide this path in any bounce messages though.
  directory_transport = maildir_internal
  hide_child_in_errmsg


# Any local address which is not matched above will be bounced.

end



######################################################################
#                      ROUTERS CONFIGURATION                         #
#            Specifies how remote addresses are handled              #
######################################################################
#                          ORDER DOES MATTER                         #
#  A remote address is passed to each in turn until it is accepted.  #
######################################################################

# Remote addresses are those with a domain that does not match any item
# in the "local_domains" setting above.


# On an MX receiver most outgoing mail is bounces. We don't want to have
# a large queue of mail waiting to be sent outwards, so if you have a
# reliable smarthost cluster then you can punt all outgoing mail straight
# to it by uncommenting the following router.

# smarthost:
#   driver = domainlist
#   route_list = "* smtp.example.com byname"
#   transport = remote_smtp


# This router routes to remote hosts over SMTP using a DNS lookup with
# default options.

lookuphost:
  driver = lookuphost
  transport = remote_smtp
  # Some silly domains point MX records at 127.0.0.1 which ends up
  # freezing the message. The following setting discards these MX records.
  ignore_target_hosts = 127.0.0.0/8

end



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

# The first retry rule says that mail to an overquota mailbox should be
# bounced immediately.

# The second 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 8 hours until 4 days have passed since the first
# failed delivery.

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

*                      quota
*                      *           F,2h,15m; G,16h,1h,1.5; F,4d,8h

end



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

# There are no rewriting specifications in this configuration file.

end



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

# There are no authenticator specifications in this configuration file.

# End of Exim configuration file