infra/pastila/smtp.nix

{ config, lib, pkgs, ... }:

let
  opendkim_selector = "21062024";
  exim = pkgs.exim.override {
    enableAuthDovecot = true;
  };
in
{
  services.opendkim = {
    enable = true;
    selector = opendkim_selector;
    domains = "csl:isomorphis.me,tremeg.net,gueneau.me";
  };

  users.groups."vmail" = {};
  users.users."vmail" = {
    isSystemUser = true;
    group = "vmail";
    home = "/var/vmail";
  };

  users.users."exim".extraGroups = [
    config.services.opendkim.group
  ];

  services.exim = {
    enable = true;
    package = exim;
    config = ''
######################################################################
#                    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 = pastila.isomorphis.me

# 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 = @ : isomorphis.me : tremeg.net : gueneau.me : armael.net
domainlist relay_to_domains = polyno.me
hostlist   relay_from_hosts = 127.0.0.1
hostlist   host_auth_accept_relay = *

# 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 Lists (ACLs) which appear 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 lists for
# checking incoming messages. The names of these ACLs are defined here:

acl_smtp_rcpt = acl_check_rcpt
acl_smtp_data = acl_check_spam

# You should not change those settings until you understand how ACLs work.


# If you are running a version of Exim that was compiled with the content-
# scanning extension, you can cause incoming messages to be automatically
# scanned for viruses. You have to modify the configuration in two places to
# set this up. The first of them is here, where you define the interface to
# your scanner. This example is typical for ClamAV; see the manual for details
# of what to set for other virus scanners. The second modification is in the
# acl_check_data access control list (see below).

# av_scanner = clamd:/tmp/clamd


# For spam scanning, there is a similar option that defines the interface to
# SpamAssassin. You do not need to set this if you are using the default, which
# is shown in this commented example. As for virus scanning, you must also
# modify the acl_check_data access control list to enable spam scanning.

# spamd_address = 127.0.0.1 11333 variant=rspamd


# If Exim is compiled with support for TLS, you may want to enable the
# following options so that Exim allows clients to make encrypted
# connections. In the authenticators section below, there are template
# configurations for plaintext username/password authentication. This kind
# of authentication is only safe when used within a TLS connection, so the
# authenticators will only work if the following TLS settings are turned on
# as well.

# Allow any client to use TLS.

tls_advertise_hosts = *

# Specify the location of the Exim server's TLS certificate and private key.
# The private key must not be encrypted (password protected). You can put
# the certificate and private key in the same file, in which case you only
# need the first setting, or in separate files, in which case you need both
# options.

tls_certificate = ${config.security.acme.certs."smtp".directory + "/cert.pem"}
tls_privatekey = ${config.security.acme.certs."smtp".directory + "/key.pem"}

# (use the defaults as those are most likely outdated)
# openssl_options = +no_sslv2 +no_sslv3
# tls_require_ciphers = HIGH:!DES:!RC4:!MD5


# In order to support roaming users who wish to send email from anywhere,
# you may want to make Exim listen on other ports as well as port 25, in
# case these users need to send email from a network that blocks port 25.
# The standard port for this purpose is port 587, the "message submission"
# port. See RFC 4409 for details. Microsoft MUAs cannot be configured to
# talk the message submission protocol correctly, so if you need to support
# them you should also allow TLS-on-connect on the traditional but
# non-standard port 465.

daemon_smtp_ports = 25 : 465 : 587
tls_on_connect_ports = 465

# 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 = isomorphis.me


# 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 users specified by
# never_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. There is an even stronger safety catch in the form of the
# FIXED_NEVER_USERS setting in the configuration for building Exim. The list of
# users that it specifies is built into the binary, and cannot be changed. The
# option below just adds additional users to the list. The default for
# FIXED_NEVER_USERS is "root", but just to be absolutely sure, the default here
# is also "root".

# 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 SMTP sessions. (The default was
# reduced from 30s to 5s for release 4.61.)

rfc1413_hosts =
# rfc1413_query_timeout = 5s


# 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


# By default, messages that are waiting on Exim's queue are all held in a
# single directory called "input" which it itself within Exim's spool
# directory. (The default spool directory is specified when Exim is built, and
# is often /var/spool/exim/.) Exim works best when its queue is kept short, but
# there are circumstances where this is not always possible. If you uncomment
# the setting below, messages on the queue are held in 62 subdirectories of
# "input" instead of all in the same directory. The subdirectories are called
# 0, 1, ... A, B, ... a, b, ... z. This has two benefits: (1) If your file
# system degrades with many files in one directory, this is less likely to
# happen; (2) Exim can process the queue one subdirectory at a time instead of
# all at once, which can give better performance with large queues.

# split_spool_directory = true


# If you're in a part of the world where ASCII is not sufficient for most
# text, then you're probably familiar with RFC2047 message header extensions.
# By default, Exim adheres to the specification, including a limit of 76
# characters to a line, with encoded words fitting within a line.
# If you wish to use decoded headers in message filters in such a way
# that successful decoding of malformed messages matters, you may wish to
# configure Exim to be more lenient.
#
# check_rfc2047_length = false
#
# In particular, the Exim maintainers have had multiple reports of problems
# from Russian administrators of issues until they disable this check,
# because of some popular, yet buggy, mail composition software.


# If you wish to be strictly RFC compliant, or if you know you'll be
# exchanging email with systems that are not 8-bit clean, then you may
# wish to disable advertising 8BITMIME.  Uncomment this option to do so.

# accept_8bitmime = false

slow_lookup_log = 500
log_selector = +ident_timeout

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

begin acl

# .include /etc/mail/acl-greylist-sqlite

# 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 = :
          control = dkim_disable_verify

  #############################################################################
  # The following section of the ACL is concerned with local parts that contain
  # @ or % or ! or / or | or dots in unusual places.
  #
  # The characters other than dots are rarely found in genuine local parts, but
  # are often tried by people looking to circumvent relaying restrictions.
  # Therefore, although they are valid in local parts, these rules lock them
  # out, as a precaution.
  #
  # Empty components (two dots in a row) are not valid in RFC 2822, but Exim
  # allows them because they have been encountered. (Consider local parts
  # constructed as "firstinitial.secondinitial.familyname" when applied to
  # someone like me, who has no second initial.) However, a local part starting
  # with a dot or containing /../ can cause trouble if it is used as part of a
  # file name (e.g. for a mailing list). This is also true for local parts that
  # contain slashes. A pipe symbol can also be troublesome if the local part is
  # incorporated unthinkingly into a shell command line.
  #
  # Two different rules are used. The first one is stricter, and is applied to
  # messages that are addressed to one of the local domains handled by this
  # host. The line "domains = +local_domains" restricts it to domains that are
  # defined by the "domainlist local_domains" setting above. The rule  blocks
  # local parts that begin with a dot or contain @ % ! / or |. If you have
  # local accounts that include these characters, you will have to modify this
  # rule.

  deny    message       = Restricted characters in address
          domains       = +local_domains
          local_parts   = ^[.] : ^.*[@%!/|]

  # The second rule applies to all other domains, and is less strict. The line
  # "domains = !+local_domains" restricts it to domains that are NOT defined by
  # the "domainlist local_domains" setting above. The exclamation mark is a
  # negating operator. This rule allows your own users to send outgoing
  # messages to sites that use slashes and vertical bars in their local parts.
  # It blocks local parts that begin with a dot, slash, or vertical bar, but
  # allows these characters within the local part. However, the sequence /../
  # is barred. The use of @ % and ! is blocked, as before. The motivation here
  # is to prevent your users (or your users' viruses) from mounting certain
  # kinds of attack on remote sites.

  deny    message       = Restricted characters in address
          domains       = !+local_domains
          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

  # Accept if the message comes from one of the hosts for which we are an
  # outgoing relay. It is assumed that such hosts are most likely to be MUAs,
  # so we set control=submission to make Exim treat the message as a
  # submission. It will fix up various errors in the message, for example, the
  # lack of a Date: header line. If you are actually relaying out out from
  # MTAs, you may want to disable this. If you are handling both relaying from
  # MTAs and submissions from MUAs you should probably split them into two
  # lists, and handle them differently.

  # 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.

  # Note that, by putting this test before any DNS black list checks, you will
  # always accept from these hosts, even if they end up on a black list. The
  # assumption is that they are your friends, and if they get onto a black
  # list, it is a mistake.

  accept  hosts         = +relay_from_hosts
          control       = submission
          control       = dkim_disable_verify

  # Accept if the message arrived over an authenticated connection, from
  # any host. Again, these messages are usually from MUAs, so recipient
  # verification is omitted, and submission mode is set. And again, we do this
  # check before any black list tests.

  accept  authenticated = *
          control       = submission/sender_retain
          control       = dkim_disable_verify

  # Insist that any other recipient address that we accept is either in one of
  # our local domains, or is in a domain for which we explicitly allow
  # relaying. Any other domain is rejected as being unacceptable for relaying.

  require message = relay not permitted
          domains = +local_domains : +relay_to_domains

  # We also require all accepted addresses to be verifiable. This check will
  # do local part verification for local domains, but only check the domain
  # for remote domains. The only way to check local parts for the remote
  # relay domains is to use a callout (add /callout), but please read the
  # documentation about callouts before doing this.

  require verify = recipient

  #############################################################################
  # There are no default 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 can get Exim to perform a DNS black list lookup at this
  # point. The first one denies, whereas 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    dnslists      = black.list.example
  #         add_header    = X-Warning: $sender_host_address is in a black list at $dnslist_domain
  #         log_message   = found in $dnslist_domain
  #############################################################################

  #############################################################################
  # This check is commented out because it is recognized that not every
  # sysadmin will want to do it. If you enable it, the check performs
  # Client SMTP Authorization (csa) checks on the sending host. These checks
  # do DNS lookups for SRV records. The CSA proposal is currently (May 2005)
  # an Internet draft. You can, of course, add additional conditions to this
  # ACL statement to restrict the CSA checks to certain hosts only.
  #
  # require verify = csa
  #############################################################################

  # At this point, the address has passed all the checks that have been
  # configured, so we accept it unconditionally.

  accept

# This ACL is used after the contents of a message have been received. This
# is the ACL in which you can test a message's headers or body, and in
# particular, this is where you can invoke external virus or spam scanners.
# Some suggested ways of configuring these tests are shown below, commented
# out. Without any tests, this ACL accepts all messages. If you want to use
# such tests, you must ensure that Exim is compiled with the content-scanning
# extension (WITH_CONTENT_SCAN=yes in Local/Makefile).

acl_check_data:

  # warn  message = X-MIME-Error: $demime_reason
  #       demime = *
  #       condition = ''${if >{$demime_errorlevel}{0}{1}{0}}
  #       set acl_m_greylistreasons = Message has MIME error: $demime_reason\n$acl_m_greylistreasons

  # warn  condition = ''${if and {                                  \
  #                       {match {''${lc:$h_subject:}}{^re:}}       \
  #                       {!def:h_References:}                    \
  #                       {!def:h_In-Reply-To:}                   \
  #                    } {1}{0}}
  #       message = X-Bad-Reply: 'Re:' in Subject but no References or In-Reply-To headers
  #       set acl_m_greylistreasons = Message has 'Re:' in Subject: but neither References: nor In-Reply-To:\n$acl_m_greylistreasons

  # warn condition = ''${if !def:h_Message-ID: {1}}
  #       set acl_m_greylistreasons = Message has no Message-Id: header\n$acl_m_greylistreasons

  # warn dnslists = psbl.surriel.org
  #      set acl_m_greylistreasons = Host listed in $dnslist_domain blacklist: $dnslist_text\n$acl_m_greylistreasons

  # require acl = greylist_mail

  # Deny if the message contains a virus. Before enabling this check, you
  # must install a virus scanner and set the av_scanner option above.
  #
  # deny    malware    = *
  #         message    = This message contains a virus ($malware_name).

  # Add headers to a message if it is judged to be spam. Before enabling this,
  # you must install SpamAssassin. You may also need to set the spamd_address
  # option above.
  #
  # warn    spam       = nobody
  #         add_header = X-Spam_score: $spam_score\n\
  #                      X-Spam_score_int: $spam_score_int\n\
  #                      X-Spam_bar: $spam_bar\n\
  #                      X-Spam_report: $spam_report

  # Accept the message.

  accept

acl_check_spam:
  # do not scan messages submitted from our own hosts
  # +relay_from_hosts is assumed to be a list of hosts in configuration
  accept hosts = +relay_from_hosts

  # do not scan messages from submission port (or maybe you want to?)
  accept condition = ''${if eq{$interface_port}{587}}

  # skip scanning for authenticated users (if desired?)
  accept authenticated = *

  # add spam-score and spam-report header when told by rspamd
  warn  spam       = nobody:true
        condition  = ''${if eq{$spam_action}{add header}}
        add_header = X-Spam-Score: $spam_score ($spam_bar)
        add_header = X-Spam-Report: $spam_report

  # $spam_action is the action recommended by rspamd
  # $spam_score is the message score (we unlikely need it)
  # $spam_score_int is spam score multiplied by 10
  # $spam_report lists symbols matched & protocol messages
  # $spam_bar is a visual indicator of spam/ham level

  # use greylisting available in rspamd v1.3+
  defer message    = Please try again later
        condition  = ''${if eq{$spam_action}{soft reject}}

  deny  message    = Message discarded as high-probability spam
        condition  = ''${if eq{$spam_action}{reject}}

  accept

######################################################################
#                      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. The exclamation mark that appears in "domains = !
# +local_domains" is a negating operator, that is, it can be read as "not". The
# recipient's domain must not be one of those defined by "domainlist
# local_domains" above for this router to be used.
#
# If the router is used, 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
  no_more


# The remaining routers handle addresses in the local domain(s), that is those
# domains that are defined by "domainlist local_domains" above.


# This router handles aliasing using a linearly searched alias file with the
# name /etc/mail/aliases. When this configuration is installed automatically,
# the name gets inserted into this file from whatever is set in Exim's
# build-time configuration. The default path is the traditional /etc/mail/aliases.
# If you install this configuration by hand, you need to specify the correct
# path in the "data" setting below.
#
##### NB  You must ensure that the alias file 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/secrets/exim/aliases}}
# user = exim
  file_transport = address_file
  pipe_transport = address_pipe

# This router handles forwarding using traditional .forward files in users'
# home directories. If you want it also to allow mail filtering when a forward
# file starts with the string "# Exim filter" or "# Sieve filter", uncomment
# the "allow_filter" option.

# The no_verify setting means that this router is skipped when Exim is
# verifying addresses. Similarly, no_expn means that this router is skipped if
# Exim is processing an EXPN command.

# If you want this router to treat local parts with suffixes introduced by "-"
# or "+" characters as if the suffixes did not exist, uncomment the two local_
# part_suffix options. Then, for example, xxxx-foo@your.domain will be treated
# in the same way as xxxx@your.domain by this router. Because this router is
# not used for verification, if you choose to uncomment those options, then you
# will *need* to make the same change to the localuser router.  (There are
# other approaches, if this is undesirable, but they add complexity).

# The check_ancestor option means that if the forward file generates an
# address that is an ancestor of the current one, the current one gets
# passed on instead. This covers the case where A is aliased to B and B
# has a .forward file pointing to A.

# The three transports specified at the end are those that are used when
# forwarding generates a direct delivery to a file, or to a pipe, or sets
# up an auto-reply, respectively.

# userforward:
#   driver = redirect
#   check_local_user
# # local_part_suffix = +* : -*
# # local_part_suffix_optional
#   file = $home/.forward
# # allow_filter
#   no_verify
#   no_expn
#   check_ancestor
#   file_transport = address_file
#   pipe_transport = address_pipe
#   reply_transport = address_reply

# Virtual users/domains

virtual:
  driver = redirect
  domains = dsearch;/etc/secrets/exim/virtual
#  data = ''${lookup{$local_part}wildlsearch{/etc/secrets/exim/virtual/$domain}}
  data = ''${lookup{$local_part}wildlsearch{/etc/secrets/exim/virtual/''${lookup{$domain}lsearch{/etc/secrets/exim/domains/domains}}}}

my_domains:
  driver = accept
  domains = dsearch;/etc/secrets/exim/domains
#  local_parts = lsearch;/etc/secrets/exim/domains/$domain
  local_parts = lsearch;/etc/secrets/exim/domains/''${lookup{$domain}lsearch{/etc/secrets/exim/domains/domains}}
  transport = my_mailboxes

# This router matches local user mailboxes. If the router fails, the error
# message is "Unknown user".

# If you want this router to treat local parts with suffixes introduced by "-"
# or "+" characters as if the suffixes did not exist, uncomment the two local_
# part_suffix options. Then, for example, xxxx-foo@your.domain will be treated
# in the same way as xxxx@your.domain by this router.

localuser:
  driver = accept
  check_local_user
# local_part_suffix = +* : -*
# local_part_suffix_optional
  transport = local_delivery
  cannot_route_message = Unknown user


######################################################################
#                      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
#  hosts_require_tls = *
  dkim_domain = $sender_address_domain
  dkim_selector = ${opendkim_selector}
  dkim_private_key = /var/lib/opendkim/keys/${opendkim_selector}.private
  dkim_canon = relaxed
  dkim_strict = 0
  headers_add = X-Clacks-Overhead: "GNU Terry Pratchett"


# 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

# Virtual users/domains

my_mailboxes:
  driver = appendfile
  maildir_format = true
  mode_fail_narrower = false
  envelope_to_add = true
  return_path_add = true
  mode = 0600
#  directory = /var/vmail/''${lookup{$domain}lsearch{/etc/secrets/exim/domains/domains}}/$local_part/Maildir
  directory = /var/vmail/$domain_data/''${lookup{$local_part}dsearch{/var/vmail/$domain_data}}/Maildir
  create_directory = true
  user = vmail

######################################################################
#                      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.

# WARNING: If you do not have any retry rules at all (this section of the
# configuration is non-existent or empty), Exim will not do any retries of
# messages that fail to get delivered at the first attempt. The effect will
# be to treat temporary errors as permanent. Therefore, DO NOT remove this
# retry rule unless you really don't want any retries.

# Address or 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                     #
######################################################################

# The following authenticators support plaintext username/password
# authentication using the standard PLAIN mechanism and the traditional
# but non-standard LOGIN mechanism, with Exim acting as the server.
# PLAIN and LOGIN are enough to support most MUA software.
#
# These authenticators are not complete: you need to change the
# server_condition settings to specify how passwords are verified.
# They are set up to offer authentication to the client only if the
# connection is encrypted with TLS, so you also need to add support
# for TLS. See the global configuration options section at the start
# of this file for more about TLS.
#
# The default RCPT ACL checks for successful authentication, and will accept
# messages from authenticated users from anywhere on the Internet.

begin authenticators

# PLAIN authentication has no server prompts. The client sends its
# credentials in one lump, containing an authorization ID (which we do not
# use), an authentication ID, and a password. The latter two appear as
# $auth2 and $auth3 in the configuration and should be checked against a
# valid username and password. In a real configuration you would typically
# use $auth2 as a lookup key, and compare $auth3 against the result of the
# lookup, perhaps using the crypteq{}{} condition.

#PLAIN:
#  driver                     = plaintext
#  server_set_id              = $auth2
#  server_prompts             = :
#  server_condition           = Authentication is not yet configured
#  server_advertise_condition = ''${if def:tls_cipher }

# plain:
#   driver = plaintext
#   public_name = PLAIN
#   server_advertise_condition = ''${if eq{$tls_cipher}{}{false}{true}}
#   server_prompts = :
#   server_set_id = $auth2
#   server_condition = \
#     ''${lookup{$2}wildlsearch{/etc/mail/passwd}\
#       {''${if crypteq{$3}{\{sha1\}''${extract{1}{:}{$value}{$value}fail}}\
#         {yes}{no}}\
#       }\
#      }

# LOGIN authentication has traditional prompts and responses. There is no
# authorization ID in this mechanism, so unlike PLAIN the username and
# password are $auth1 and $auth2. Apart from that you can use the same
# server_condition setting for both authenticators.

#LOGIN:
#  driver                     = plaintext
#  server_set_id              = $auth1
#  server_prompts             = <| Username: | Password:
#  server_condition           = Authentication is not yet configured
#  server_advertise_condition = ''${if def:tls_cipher }

# login:
#   driver = plaintext
#   public_name = LOGIN
#   server_advertise_condition = ''${if eq{$tls_cipher}{}{false}{true}}
#   server_prompts = Username:: : Password::
#   server_set_id = $auth1
#   server_condition = \
#     ''${lookup{$1}wildlsearch{/etc/mail/passwd}\
#       {''${if crypteq{$2}{\{sha1\}''${extract{1}{:}{$value}{$value}fail}}\
#         {yes}{no}}\
#       }\
#      }

dovecot_plain:
  driver = dovecot
  public_name = PLAIN
  server_socket = /var/run/dovecot2/auth-client
  server_set_id = $auth2


######################################################################
#                   CONFIGURATION FOR local_scan()                   #
######################################################################

# If you have built Exim to include a local_scan() function that contains
# tables for private options, you can define those options here. Remember to
# uncomment the "begin" line. It is commented by default because it provokes
# an error with Exim binaries that are not built with LOCAL_SCAN_HAS_OPTIONS
# set in the Local/Makefile.

# begin local_scan

# End of exim configuration.
'';
  };

  security.acme.certs."smtp" = {
    domain = "smtp.isomorphis.me";
    extraDomainNames = [
      "smtp.tremeg.net"
      "smtp.gueneau.me"
    ];
    group = config.services.exim.group;
  };

  # FIXME
  environment.systemPackages = [ pkgs.acl ];
  system.activationScripts."secrets-permissions" = lib.mkForce ''
    # Default to restrictive permissions on secrets.
    # Root can alway read/write/traverse directories no matter the permissions
    # set.

    mkdir -p /etc/secrets

    chown --recursive root:root /etc/secrets
    chmod --recursive 600 /etc/secrets

    # Relax permissions on some secrets.

    # The top directory must be readable and traversable by thoses who need to
    # access secrets.
    chmod 755 /etc/secrets

    mkdir -p /etc/secrets/exim/virtual
    mkdir -p /etc/secrets/exim/domains
    chmod 700 /etc/secrets/exim
    chmod 700 /etc/secrets/exim/virtual
    chmod 700 /etc/secrets/exim/domains
    chown --recursive ${config.services.exim.user}:${config.services.exim.group} /etc/secrets/exim

    mkdir -p /etc/secrets/dovecot
    chmod -R 700 /etc/secrets/dovecot
    chown --recursive ${config.services.dovecot2.user}:${config.services.dovecot2.group} /etc/secrets/dovecot

    # XXX clean this up
    chmod g+r /var/lib/opendkim/keys/${opendkim_selector}.private
    chmod g+rx /var/lib/opendkim/
    ${pkgs.acl}/bin/setfacl -m g:exim:x /var/lib/opendkim/
    ${pkgs.acl}/bin/setfacl -m g:exim:x /var/lib/opendkim/keys/
    ${pkgs.acl}/bin/setfacl -m g:exim:r /var/lib/opendkim/keys/21062024.private 
  '';
}