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+# Modified from https://www.c0ffee.net/blog/mail-server-guide
+
+smtpd_banner = $myhostname ESMTP dx Independence
+
+# "2" is current for postfix 3.2 configs
+compatibility_level = 2
+
+# disable "new mail" notifications for local unix users
+biff = no
+
+# directory to store mail for local unix users
+mail_spool_directory = /var/mail/local
+
+# Name of this mail server, used in the SMTP HELO for outgoing mail. Make
+# sure this resolves to the same IP as your reverse DNS hostname.
+myhostname = {{ network.hostname.public }}
+
+# Domains for which postfix will deliver local mail. Does not apply to
+# virtual domains, which are configured below. Make sure to specify the FQDN
+# of your sever, as well as localhost.
+# Note: NEVER specify any virtual domains here!!! Those come later.
+mydestination = localhost
+
+# Domain appended to mail sent locally from this machine - such as mail sent
+# via the `sendmail` command.
+myorigin = $myhostname
+
+# prevent spammers from searching for valid users
+disable_vrfy_command = yes
+
+# require properly formatted email addresses - prevents a lot of spam
+strict_rfc821_envelopes = yes
+
+# don't give any helpful info when a mailbox doesn't exist
+show_user_unknown_table_name = no
+
+# limit maximum e-mail size to 256 MB. mailbox size must be at least as big as
+# the message size for the mail to be accepted, but has no meaning after
+# that since we are using Dovecot for delivery.
+message_size_limit = 268435456
+mailbox_size_limit = 0
+
+# require addresses of the form "[email protected]"
+allow_percent_hack = no
+swap_bangpath = no
+
+# allow plus-aliasing: "[email protected]" delivers to "user" mailbox
+recipient_delimiter = +
+
+# path to the SSL certificate for the mail server
+smtpd_tls_cert_file = /etc/ssl/{{ network.hostname.public }}-cert-combined.rsa2048.pem
+smtpd_tls_key_file = /etc/ssl/private/{{ network.hostname.public }}-key.rsa2048.pem
+
+# You can also specify an EC cert to try first if the clients support it.
+smtpd_tls_eccert_file = /etc/ssl/{{ network.hostname.public }}-cert-combined.prime256v1.pem
+smtpd_tls_eckey_file = /etc/ssl/private/{{ network.hostname.public }}-key.prime256v1.pem
+
+# Path to your trusted certificates file. Usually provided by a
+# ca-certificates package or similar.
+smtp_tls_CAfile=/etc/ssl/certs/ca-certificates.crt
+
+# These two lines define how postfix will connect to other mail servers.
+# "may" allows opportunistic TLS and "enabled" allows hostname lookups
+# http://www.postfix.org/TLS_README.html
+smtp_tls_security_level = may
+smtp_dns_support_level = enabled
+
+# IP address used by postfix to send outgoing mail. You only need this if
+# your machine has multiple IP addresses - set it to your MX address to
+# satisfy your SPF record.
+smtp_bind_address = {{ hostvars[inventory_hostname]['ansible_' + network.interface.public]['ipv4']['address'] }}
+smtp_bind_address6 =
+inet_interfaces = 127.0.0.1,$smtp_bind_address
+inet_protocols = ipv4
+
+# Here we define the options for "mandatory" TLS. In our setup, TLS is only
+# "mandatory" for authenticating users. I got these settings from Mozilla's
+# SSL reccomentations page.
+#
+# NOTE: do not attempt to make TLS mandatory for all incoming/outgoing
+# connections. Do not attempt to change the default cipherlist for non-
+# mandatory connections either. There are still a lot of mail servers out
+# there that do not use TLS, and many that do only support old ciphers.
+# Forcing TLS for everyone *will* cause you to lose mail.
+smtpd_tls_mandatory_protocols = !SSLv2, !SSLv3, !TLSv1, !TLSv1.1, TLSv1.2
+smtpd_tls_mandatory_ciphers = high
+tls_high_cipherlist = ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-SHA384:ECDHE-RSA-AES256-SHA384:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA256
+
+# allow other mail servers to connect using TLS, but don't require it
+smtpd_tls_security_level = may
+
+# tickets and compression have known vulnerabilities
+tls_ssl_options = no_ticket, no_compression
+
+# yes, using 2048 with "dh1024" is the right thing to do
+smtpd_tls_dh1024_param_file = /etc/ssl/ffdhe2048.pem
+
+# cache incoming and outgoing TLS sessions
+smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_tlscache
+smtp_tls_session_cache_database  = btree:${data_directory}/smtp_tlscache
+
+# enable SMTPD auth. Dovecot will place an `auth` socket in postfix's
+# runtime directory that we will use for authentication.
+# TODO: can also replace this with a network inet connection if dovecot opens it
+smtpd_sasl_auth_enable = yes
+smtpd_sasl_path = private/auth
+smtpd_sasl_type = dovecot
+
+# only allow authentication over TLS
+smtpd_tls_auth_only = yes
+
+# don't allow plaintext auth methods on unencrypted connections
+smtpd_sasl_security_options = noanonymous, noplaintext
+# but plaintext auth is fine when using TLS
+smtpd_sasl_tls_security_options = noanonymous
+
+# add a message header when email was recieved over TLS
+smtpd_tls_received_header = yes
+
+# require that connecting mail servers identify themselves - this greatly
+# reduces spam
+smtpd_helo_required = yes
+
+# The following block specifies some security restrictions for incoming
+# mail. The gist of it is, authenticated users and connections from
+# localhost can do anything they want. Random people connecting over the
+# internet are treated with more suspicion: they must have a reverse DNS
+# entry and present a valid, FQDN HELO hostname. In addition, they can only
+# send mail to valid mailboxes on the server, and the sender's domain must
+# actually exist.
+smtpd_client_restrictions =
+  permit_mynetworks,
+  permit_sasl_authenticated,
+  #reject_unknown_reverse_client_hostname,
+  # you might want to consider:
+  #  reject_unknown_client_hostname,
+  # here. This will reject all incoming connections without a reverse DNS
+  # entry that resolves back to the client's IP address. This is a very
+  # restrictive check and may reject legitimate mail.
+  reject_unauth_pipelining
+smtpd_helo_restrictions =
+  permit_mynetworks,
+  permit_sasl_authenticated,
+  reject_invalid_helo_hostname,
+  reject_non_fqdn_helo_hostname,
+  # you might want to consider:
+  #  reject_unknown_helo_hostname,
+  # here. This will reject all incoming mail without a HELO hostname that
+  # properly resolves in DNS. This is a somewhat restrictive check and may
+  # reject legitimate mail.
+  reject_unauth_pipelining
+smtpd_sender_restrictions =
+  permit_mynetworks,
+  permit_sasl_authenticated,
+  reject_non_fqdn_sender,
+#  reject_unknown_sender_domain,
+  reject_unauth_pipelining
+smtpd_relay_restrictions =
+  permit_mynetworks,
+  permit_sasl_authenticated,
+  # !!! THIS SETTING PREVENTS YOU FROM BEING AN OPEN RELAY !!!
+  reject_unauth_destination
+  # !!!      DO NOT REMOVE IT UNDER ANY CIRCUMSTANCES      !!!
+#smtpd_recipient_restrictions =
+#  permit_mynetworks,
+#  permit_sasl_authenticated,
+#  reject_non_fqdn_recipient,
+#  reject_unknown_recipient_domain,
+#  reject_unauth_pipelining,
+smtpd_data_restrictions =
+  permit_mynetworks,
+  permit_sasl_authenticated,
+  reject_multi_recipient_bounce,
+  reject_unauth_pipelining
+
+smtpd_recipient_restrictions =
+    permit_mynetworks,
+    permit_sasl_authenticated,
+    reject_unauth_destination
+
+# deliver mail for virtual users to Dovecot's LMTP socket
+# TODO: convert this to network with dovecot opening a local inet port
+virtual_transport = lmtp:unix:private/dovecot-lmtp
+virtual_mailbox_domains = /etc/postfix/domains
+
+virtual_alias_maps = hash:/etc/postfix/virtual
+#virtual_alias_domains = /etc/postfix/domains
+
+# We'll uncomment these when we set up rspamd later:
+milter_protocol = 6
+milter_default_action = accept
+#smtpd_milters = unix:/var/run/rspamd/milter.sock
+smtpd_milters = inet:localhost:11332
+milter_mail_macros = i {mail_addr} {client_addr} {client_name} {auth_authen}