# See /usr/share/postfix/main.cf.dist for a commented, more complete version

smtpd_banner = $myhostname ESMTP
biff = no
append_dot_mydomain = no
readme_directory = no

# Basic configuration
# myhostname =
alias_maps = hash:/etc/aliases
alias_database = hash:/etc/aliases
# Take the following concerns into consideration if adjusting `mydestination`:
# https://github.com/docker-mailserver/docker-mailserver/pull/3264#pullrequestreview-1396816109
# https://github.com/docker-mailserver/docker-mailserver/pull/3264#issuecomment-1518993555
mydestination = $myhostname, localhost.$mydomain, localhost
relayhost =
mynetworks = 127.0.0.0/8 [::1]/128 [fe80::]/64
mailbox_size_limit = 0
recipient_delimiter = +
inet_interfaces = all
inet_protocols = all

# TLS parameters
# These [snakeoil files actually exist](https://askubuntu.com/questions/396120/what-is-the-purpose-of-the-ssl-cert-snakeoil-key), but shouldn't ever be used in production!
# If no `SSL_TYPE` env is set, "plaintext" is configured, but still accepts SSL with these:
smtpd_tls_chain_files = /etc/ssl/private/ssl-cert-snakeoil.key /etc/ssl/certs/ssl-cert-snakeoil.pem
#smtpd_tls_CAfile =
#smtp_tls_CAfile =
smtpd_tls_security_level = may
smtpd_tls_loglevel = 1
smtp_tls_security_level = may
smtp_tls_loglevel = 1

# Reduces CPU overhead with `NO_COMPRESSION`, SMTP not at risk of CRIME attack (see git blame for details)
# Reduce opportunities for a potential CPU exhaustion attack with `NO_RENEGOTIATION`
tls_ssl_options = NO_COMPRESSION, NO_RENEGOTIATION

tls_high_cipherlist = 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
tls_preempt_cipherlist = yes
smtpd_tls_protocols = !SSLv2,!SSLv3,!TLSv1,!TLSv1.1
smtp_tls_protocols = !SSLv2,!SSLv3,!TLSv1,!TLSv1.1
smtpd_tls_mandatory_ciphers = high
smtpd_tls_mandatory_protocols = !SSLv2,!SSLv3,!TLSv1,!TLSv1.1
smtpd_tls_exclude_ciphers = aNULL, SEED, CAMELLIA, RSA+AES, SHA1
smtpd_tls_dh1024_param_file = /etc/postfix/dhparams.pem
smtpd_tls_CApath = /etc/ssl/certs
smtp_tls_CApath = /etc/ssl/certs

# Settings to prevent SPAM early
smtpd_helo_required = yes
smtpd_delay_reject = yes
smtpd_helo_restrictions = permit_mynetworks, reject_invalid_helo_hostname, permit
smtpd_relay_restrictions = permit_mynetworks permit_sasl_authenticated defer_unauth_destination
smtpd_recipient_restrictions = permit_sasl_authenticated, permit_mynetworks, reject_unauth_destination, reject_unauth_pipelining, reject_invalid_helo_hostname, reject_non_fqdn_helo_hostname, reject_unknown_recipient_domain
smtpd_client_restrictions = permit_mynetworks, permit_sasl_authenticated, reject_unauth_destination, reject_unauth_pipelining
smtpd_sender_restrictions = $dms_smtpd_sender_restrictions
smtpd_discard_ehlo_keywords = silent-discard, dsn
disable_vrfy_command = yes

# Custom defined parameters for DMS:
dms_smtpd_sender_restrictions = permit_sasl_authenticated, permit_mynetworks, reject_unknown_sender_domain
# Submission ports 587 and 465 support for SPOOF_PROTECTION=1
mua_sender_restrictions = reject_authenticated_sender_login_mismatch, $dms_smtpd_sender_restrictions

# Postscreen settings to drop zombies/open relays/spam early
postscreen_dnsbl_action = enforce
postscreen_dnsbl_sites =
    zen.spamhaus.org=127.0.0.[2..11]*3
    bl.mailspike.net=127.0.0.[2;14;13;12;11;10]
    b.barracudacentral.org*2
    bl.spameatingmonkey.net=127.0.0.2
    dnsbl.sorbs.net
    psbl.surriel.com
    list.dnswl.org=127.0.[0..255].0*-2
    list.dnswl.org=127.0.[0..255].1*-3
    list.dnswl.org=127.0.[0..255].[2..3]*-4
postscreen_dnsbl_threshold = 3
postscreen_dnsbl_whitelist_threshold = -1
postscreen_greet_action = enforce
postscreen_bare_newline_action = enforce

# SASL
smtpd_sasl_auth_enable = no
smtpd_sasl_path = /dev/shm/sasl-auth.sock
smtpd_sasl_type = dovecot

smtpd_sasl_security_options = noanonymous
smtpd_sasl_local_domain = $mydomain
broken_sasl_auth_clients = yes

# Mail directory
virtual_transport = lmtp:unix:/var/run/dovecot/lmtp
virtual_mailbox_domains = /etc/postfix/vhost
virtual_mailbox_maps = texthash:/etc/postfix/vmailbox
virtual_alias_maps = texthash:/etc/postfix/virtual

# Milters used by DKIM
milter_protocol = 6
milter_default_action = accept
smtpd_milters =
non_smtpd_milters =

# Header checks for content inspection on receiving
header_checks = pcre:/etc/postfix/maps/header_checks.pcre

# Remove unwanted headers that reveal our privacy
smtp_header_checks = pcre:/etc/postfix/maps/sender_header_filter.pcre

# The default compatibility_level is 0 - which retains legacy settings defaults:
# http://www.postfix.org/COMPATIBILITY_README.html
# If backwards-compaitibilty log messages appear, fix them by explicitly adding
# the legacy or new default value (alternatively raise the compatibility_level)
#
# TODO: The next compatibility_level is 3.6, when Postfix 3.6 is available consider
# bumping this value after taking the compaitibilty changes into account.
compatibility_level = 2