{ nglib, nixpkgs }:
nglib.makeSystem {
  system = "x86_64-linux";
  name = "nixng-postfix";
  inherit nixpkgs;
  config = ({ pkgs, config, ... }:
    {
      config = {
        dumb-init = {
          enable = true;
          type.services = {};
        };
        init.services.postfix = {
          shutdownOnExit = true;
        };
        services.postfix = {
          enable = true;

          masterConfig = {
            pickup = {
              type = "unix";
              private = "n";
              chroot = "n";
              wakeup = "60";
              maxproc = "1";
              command = "pickup";
            };
            cleanup = { type = "unix"; private = "n"; chroot = "n"; maxproc = "0";
                        command = "cleanup"; };
            qmgr = { type = "unix"; private = "n"; chroot = "n"; wakeup = "300";
                     maxproc = "1"; command = "qmgr"; };
            tlsmgr = { type = "unix"; wakeup = "1000?"; maxproc = 1; command = "tlsmgr"; };
            rewrite = { type = "unix"; chroot = "n"; command = "trivial-rewrite"; };
            bounce = { type = "unix"; chroot = "n";  maxproc = 0; command = "bounce"; };
            defer = { type = "unix"; chroot = "n"; maxproc = 0; command = "bounce"; };
            trace = { type = "unix"; chroot = "n"; maxproc = 0; command = "bounce"; };
            verify = { type = "unix"; chroot = "n"; maxproc = 1; command = "verify"; };
            flush = { type = "unix"; chroot = "n"; wakeup = "1000?"; maxproc = "0";
                      command = "flush"; };
            proxymap = { type = "unix"; chroot = "n"; command = "proxymap"; };
            proxywrite = { type = "unix"; chroot = "n"; maxproc = "1";
                           command = "proxymap"; };
            smtp = [ { type = "unix"; chroot = "n"; command = "smtp"; }
                     { type = "inet"; private = "n"; chroot = "n"; command = "smtpd"; }
                   ];
            relay = { type = "unix"; chroot = "n"; command = ''
              smtp
                      -o syslog_name=postfix/$service_name
              #       -o smtp_helo_timeout=5 -o smtp_connect_timeout=5
            ''; };
            showq = { type = "unix"; private = "n"; chroot = "n"; command = "showq"; };
            error = { type = "unix"; chroot = "n"; command = "error"; };
            retry = { type = "unix"; chroot = "n"; command = "error"; };
            discard = { type = "unix"; chroot = "n"; command = "discard"; };
            local = { type = "unix";  unpriv = "n"; chroot = "n"; command = "local"; };
            virtual = { type = "unix"; unpriv = "n"; chroot = "n"; command = "virtual"; };
            lmtp = { type = "unix"; chroot = "n"; command = "lmtp"; };
            anvil = { type = "unix"; chroot = "n"; maxproc = 1; command = "anvil"; };
            scache = { type = "unix"; chroot = "n"; maxproc = 1; command = "scache"; };
            postlog =
              { type = "unix-dgram"; private = "n"; chroot = "n"; maxproc = "1";
                command = "postlogd"; };
          };

          mainConfig = {
            smptd_banner = [ "$myhostname" "ESMTP" "$mail_name" "(Ubuntu)" ];
            biff = "no";
            
            # delay_warning_time = "4h";

            append_dot_mydomain = "no";

            readme_directory = "no";

            compatibility_level = 2;

            smtpd_tls_cert_file = "/etc/letsencrypt/live/example.com/fullchain.pem";
            smtpd_tls_key_file = "/etc/letsencrypt/live/example.com/privkey.pem";
            smtpd_use_tls = "yes";
            smtpd_tls_auth_only = "yes";
            smtp_tls_security_level = "may";
            smtpd_tls_security_level = "may";
            smtpd_sasl_security_options = [ "noanonymous" "noplaintext" ];
            smtpd_sasl_tls_security_options = "noanonymous";

            smtpd_sasl_type = "dovecot";
            smtpd_sasl_path = "private/auth";
            smtpd_sals_auth_enable = "yes";

            smtpd_helo_restrictions =
              [ "permit_mynetworks"
                "permit_sals_authenticated"
                "reject_invalid_helo_hostname"
                "reject_non_fqdn_helo_hostname"
              ];
            smtpd_recipient_restrictions =
              [ "permit_mynetworks"
                "permit_sasl_authenticated"
                "reject_non_fqdn_recipient"
                "reject_unknown_recipient_domain"
                "reject_unlisted_recipient"
                "reject_unauth_destination"
              ];
            smtpd_sender_restrictions =
              [ "permit_mynetworks"
                "permit_sasl_authenticated"
                "reject_non_fqdn_sender"
                "reject_unknown_sender_domain"
              ];
            smtpd_relay_restrictions =
              [ "permit_mynetworks"
                "permit_sasl_authenticated"
                "defer_unauth_destination"
              ];

            myhostname = "example.org";
            alias_maps = "hash:/etc/aliases";
            alias_database = "hash:/etc/aliases";
            mydoamin = "example.org";
            myorigin = "$mydomain";
            mydestination = "localhost";
            relayhost = "";
            mynetworks =
              [ "127.0.0.0/8"
                "[::ffff:127.0.0.0]/104"
                "[::1]/128"
              ];
            mailbox_size_limit = 0;
            recipient_delimiter = "+";
            inet_interfaces = "all";
            inet_protocols = "all";

            virtual_transport = "lmtp:unix:private/dovecot-lmtp";

            virtual_mailbox_domains = "mysql:/etc/postfix/mysql-virtual-mailbox-domains.cf";
            virtual_mailbox_maps = "mysql:/etc/postfix/mysql-virtual-mailbox-maps.cf";
            virtual_alias_maps =
              [ "mysql:/etc/postfix/mysql-virtual-alias-maps.cf"
                "mysql:/etc/postfix/mysql-virtual-email2email.cf"
              ];

            disable_vrfy_command = "yes";
            strict_rfc821_envelopes = "yes";
            # smtpd_etrn_restrictions = "yes";
            # smtpd_reject_unlisted_sender = "yes";
            # smtpd_reject_unlisted_recipient = "yes";
            smtpd_delay_reject = "yes";
            smtpd_helo_required = "yes";
            smtp_always_send_ehlo = "yes";
            # smtpd_hard_error_limit = 1;
            smtpd_timeout = "30s";
            smtp_helo_timeout = "15s";
            smtp_rcpt_timeout = "15s";
            smtpd_recipient_limit = "15s";
            minimal_backoff_time = "180s";
            maximal_backoff_time = "3h";

            invalid_hostname_reject_code = 550;
            non_fqdn_reject_code = 550;
            unknown_address_reject_code = 550;
            unknown_client_reject_code = 550;
            unknown_hostname_reject_code = 550;
            unverified_recipent_reject_code = 550;
            unverified_sender_reject_code = 550;
          };
        };
      };
    });
}