# checking incoming messages. The names of these ACLs are defined here:
acl_smtp_rcpt = acl_check_rcpt
+acl_smtp_data_prdr = acl_check_prdr
acl_smtp_data = acl_check_data
# You should not change those settings until you understand how ACLs work.
# tls_certificate = /etc/ssl/exim.crt
# tls_privatekey = /etc/ssl/exim.pem
+# For OpenSSL, prefer EC- over RSA-authenticated ciphers
+# tls_require_ciphers = ECDSA:RSA:!COMPLEMENTOFDEFAULT
+
# 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.
# tls_on_connect_ports = 465
# sane defaults
-# https://wiki.mozilla.org/Security/Server_Side_TLS#Intermediate_compatibility_.28default.29
-# tls_require_ciphers = ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA256:ECDHE-ECDSA-AES128-SHA:ECDHE-RSA-AES256-SHA384:ECDHE-RSA-AES128-SHA:ECDHE-ECDSA-AES256-SHA384:ECDHE-ECDSA-AES256-SHA:ECDHE-RSA-AES256-SHA:DHE-RSA-AES128-SHA256:DHE-RSA-AES128-SHA:DHE-RSA-AES256-SHA256:DHE-RSA-AES256-SHA:ECDHE-ECDSA-DES-CBC3-SHA:ECDHE-RSA-DES-CBC3-SHA:EDH-RSA-DES-CBC3-SHA:AES128-GCM-SHA256:AES256-GCM-SHA384:AES128-SHA256:AES256-SHA256:AES128-SHA:AES256-SHA:DES-CBC3-SHA:!DSS
-# openssl_options = +no_sslv2 +no_sslv3 +no_compression
+# https://ssl-config.mozilla.org/#server=exim&version=4.93&config=intermediate&openssl=1.1.1k&guideline=5.6
+tls_require_ciphers = ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384
+openssl_options = +no_sslv2 +no_sslv3 +no_tlsv1 +no_tlsv1_1 +no_compression
# Specify the domain you want to be added to all unqualified addresses
# here. An unqualified address is one that does not contain an "@" character
host_lookup = *
-
# Advertise DSN for these hosts
#
dsn_advertise_hosts = *
+# The setting below causes Exim to try to initialize the system resolver
+# library with DNSSEC support. It has no effect if your library lacks
+# DNSSEC support.
+
+dns_dnssec_ok = 1
+
# The settings below 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
# Enable an efficiency feature. We advertise the feature; clients
# may request to use it. For multi-recipient mails we then can
# reject or accept per-user after the message is received.
+# This supports recipient-dependent content filtering; without it
+# you have to temp-reject any recipients after the first that have
+# incompatible filtering, and do the filtering in the data ACL.
+# Even with this enabled, you must support the old style for peers
+# not flagging support for PRDR (visible via $prdr_requested).
#
prdr_enable = true
# split_spool_directory = true
-
-# Wire format for spool files
-spool_wireformat = 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
require verify = sender
+ # Reject all RCPT commands after too many bad recipients
+ # This is partly a defense against spam abuse and partly attacker abuse.
+ # Real senders should manage, by the time they get to 10 RCPT directives,
+ # to have had at least half of them be real addresses.
+ #
+ # This is a lightweight check and can protect you against repeated
+ # invocations of more heavy-weight checks which would come after it.
+
+ deny condition = ${if and {\
+ {>{$rcpt_count}{10}}\
+ {<{$recipients_count}{${eval:$rcpt_count/2}}} }}
+ message = Rejected for too many bad recipients
+ logwrite = REJECT [$sender_host_address]: bad recipient count high [${eval:$rcpt_count-$recipients_count}]
+
# 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
# require verify = csa
#############################################################################
+ #############################################################################
+ # If doing per-user content filtering then recipients with filters different
+ # to the first recipient must be deferred unless the sender talks PRDR.
+ #
+ # defer !condition = $prdr_requested
+ # condition = ${if > {0}{$receipients_count}}
+ # condition = ${if !eq {$acl_m_content_filter} \
+ # {${lookup PER_RCPT_CONTENT_FILTER}}}
+ # warn !condition = $prdr_requested
+ # condition = ${if > {0}{$receipients_count}}
+ # set acl_m_content_filter = ${lookup PER_RCPT_CONTENT_FILTER}
+ #############################################################################
+
# At this point, the address has passed all the checks that have been
# configured, so we accept it unconditionally.
accept
+# This ACL is used once per recipient, for multi-recipient messages, if
+# we advertised PRDR. It can be used to perform receipient-dependent
+# header- and body- based filtering and rejections.
+# We set a variable to record that PRDR was active used, so that checking
+# in the data ACL can be skipped.
+
+acl_check_prdr:
+ warn set acl_m_did_prdr = y
+
+ #############################################################################
+ # do lookup on filtering, with $local_part@$domain, deny on filter match
+ #
+ # deny set acl_m_content_filter = ${lookup PER_RCPT_CONTENT_FILTER}
+ # condition = ...
+ #############################################################################
+
+ 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
# we should never receive one such via SMTP.
#
deny condition = ${if > {$max_received_linelength}{998}}
+ message = maximum allowed line length is 998 octets, \
+ got $max_received_linelength
+
+ # Deny if the headers contain badly-formed addresses.
+ #
+ deny !verify = header_syntax
+ message = header syntax
+ log_message = header syntax ($acl_verify_message)
# Deny if the message contains a virus. Before enabling this check, you
# must install a virus scanner and set the av_scanner option above.
# X-Spam_bar: $spam_bar\n\
# X-Spam_report: $spam_report
+ #############################################################################
+ # No more tests if PRDR was actively used.
+ # accept condition = ${if def:acl_m_did_prdr}
+ #
+ # To get here, all message recipients must have identical per-user
+ # content filtering (enforced by RCPT ACL). Do lookup for filter
+ # and deny on match.
+ #
+ # deny set acl_m_content_filter = ${lookup PER_RCPT_CONTENT_FILTER}
+ # condition = ...
+ #############################################################################
+
+
+
# Accept the message.
accept
local_delivery:
driver = appendfile
- file = /var/mail/$local_part
+ file = /var/mail/$local_part_data
delivery_date_add
envelope_to_add
return_path_add
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