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######################################################################
# ACL CONFIGURATION #
# Specifies access control lists for incoming SMTP mail #
######################################################################
begin acl
######################
# GENERAL CHECK ACLs #
######################
# Ensures that the remote host has introduced itself.
acl_check_rcpt_introduction:
# Insist that a HELO/EHLO was accepted.
require condition = ${if def:sender_helo_name}
set acl_m_msg = HELO/EHLO command required.
accept
# Syntactic validation of fields.
acl_check_rcpt_syntax:
# Deny if the local parts is malformed.
deny local_parts = ^[.] : ^.*[@%!/|]
set acl_m_msg = Invalid local part.
accept
# Checks the link between a given mail alias and a given user.
# $acl_arg1: alias to check
# $acl_arg2: user
acl_check_alias:
# Accept if the alias belongs to the user.
accept condition = ${lookup{$acl_arg1}lsearch{ALIASMAP} \
{${if eq{$value}{$acl_arg2} {yes}{no}}} {no}}
# Deny otherwise
deny
# Checks if the host is allowed to send messages according to the local whitelist, DNS blocklists and SPF policy.
acl_check_rcpt_host_policy:
# Accept all messages from trusted hosts and relays.
accept hosts = +redirected_from_hosts
# Deny messages from hosts known to be bad.
deny dnslists = sbl-xbl.spamhaus.org : bl.spamcop.net
set acl_m_msg = Rejected: $sender_host_address is in a black list at $dnslist_domain\n$dnslist_text
# Accept if the host is an authorized sender according to the SPF policy for the domain (SPF pass).
accept set acl_m_spf = ${run{/usr/bin/spfquery.mail-spf-perl \
--ip ${quote:$sender_host_address} \
--identity ${if def:sender_address_domain \
{--scope mfrom --identity ${quote:$sender_address}} \
{--scope helo --identity ${quote:$sender_helo_name}}}}}
condition = ${if eq {$acl_m_spf}{0}{yes}{no}}
# Deny if the host is explicitely not an authorized sender according to the SPF policy for the domain (SPF fail).
deny condition = ${if eq {$acl_m_spf}{1}{yes}{no}}
set acl_m_msg = [SPF] $sender_host_address is not allowed to send mail from \
${if def:sender_address_domain {$sender_address_domain}{$sender_helo_name}}. \
Please see http://www.openspf.org/Why?scope=${if def:sender_address_domain \
{mfrom}{helo}};identity=${if def:sender_address_domain \
{$sender_address}{$sender_helo_name}};ip=$sender_host_address
# Deny messages from hosts listed as non-MTA in the PBL, for which SPF couldn't determine a policy.
deny dnslists = pbl.spamhaus.org
set acl_m_msg = Rejected: $sender_host_address is in a black list at $dnslist_domain\n$dnslist_text
# Accept otherwise
accept
#########################
# MUA ACLs (submission) #
#########################
acl_mua_rcpt:
require encrypted = *
message = Encryption required.
require acl = acl_check_rcpt_introduction
message = Courtesy protocol violation: $acl_m_msg
require authenticated = *
control = submission
control = dkim_disable_verify
message = Authentication required.
require acl = acl_check_rcpt_syntax
message = Syntactic validation failed: $acl_m_msg
require verify = sender
message = Sender verification failed.
accept
acl_mua_mail:
require acl = acl_check_alias $sender_address $authenticated_id
message = Envelope address mismatch: $authenticated_id is not authorized to use $sender_address.
accept
acl_mua_data:
require acl = acl_check_alias ${address:$h_from:} $authenticated_id
message = Header address mismatch: $authenticated_id is not authorized to use ${address:$h_from:}.
accept
############
# MTA ACLs #
############
acl_mta_rcpt:
require acl = acl_check_rcpt_introduction
message = Courtesy protocol violation: $acl_m_msg
require acl = acl_check_rcpt_host_policy
message = $acl_m_msg
require acl = acl_check_rcpt_syntax
message = Syntactic validation failed: $acl_m_msg
require verify = sender
message = Sender verification failed.
require domains = +local_domains : +relay_to_domains
message = Unhandled destination.
require verify = recipient
message = Recipient verification failed.
accept
acl_mta_data:
# Deny if the message contains an overlong line. Per the standards we should never receive one such via SMTP.
deny condition = ${if > {$max_received_linelength}{998}}
set acl_m_msg = Maximum allowed line length is 998 octets, got $max_received_linelength.
accept
# Checks the validity of each signatures in the message, and the presence of a required signature for the sender domain.
# Global var to enable mandatory signature check: dkim_verify_signers = $sender_address_domain:$dkim_signers
acl_mta_dkim:
# Deny messages with invalid signatures.
deny dkim_status = fail
message = [DKIM] invalid signature ($dkim_verify_reason).
# Deny messages with no signature for domains which are explicitely requiring one.
deny dkim_status = none
condition = ${if match \
{${run{/usr/bin/dig +short TXT ${quote:_domainkey.$sender_host_address}}}}{/o=-/} \
{yes}{no}}
message = [DKIM] required signature is missing.
accept
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