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

            masterConfig = import ./master_config.nix;
            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;
            };
          };
        };
      };
  };
}