the_prg_server_configuration_old/nix-system-configs/modules/system/mail-server.nix

{
  config,
  pkgs,
  lib,
  ...
}: let
  choose = paths: lib.findFirst builtins.pathExists null paths;
  # Read secrets from sops-managed files and trim trailing newlines so the
  # generated stalwart config contains the actual secret values (not the
  # literal "$FOO" placeholders). Using builtins.readFile here ensures the
  # values are placed into the TOML at build time.
  # Use a safe helper that handles missing secret attributes or missing files
  # during a dry-run (returns empty string if absent).
  getSecret = secretAttr:
    if secretAttr != null && builtins.pathExists secretAttr.path
    then builtins.replaceStrings ["\n"] [""] (builtins.readFile secretAttr.path)
    else "";
  adminPassword = getSecret config.sops.secrets."admin-password";
  boardPassword = getSecret config.sops.secrets."board-member-password";
  utilityPassword = getSecret config.sops.secrets."utility-password";
  cloudflareUsername = getSecret config.sops.secrets."cloudflare-username";
  cloudflareToken = getSecret config.sops.secrets."cloudflare-dns-token";
in {
  options.local = {
    hostname = lib.mkOption {
      type = lib.types.str;
      default = "nixos-default";
      description = "System hostname";
    };
    username = lib.mkOption {
      type = lib.types.str;
      default = "user";
      description = "Primary user username";
    };
    userDescription = lib.mkOption {
      type = lib.types.str;
      default = "NixOS User";
      description = "Primary user description";
    };
    address = lib.mkOption {
      type = lib.types.str;
      default = "10.1.1.100";
      description = "Static IP address";
    };
  };

  imports = lib.filter (x: x != null) [
    (choose [./modules/desktop-manager/sway_greetd_homemanager.nix ../desktop-manager/sway_greetd_homemanager.nix])
    (choose [./modules/local/hostname_username.nix ../local/hostname_username.nix])
    (choose [./modules/local/networking_local.nix ../local/networking_local.nix])
    (choose [./modules/bootloader/seabios-assigned-proxmox-at-birth.nix ../bootloader/seabios-assigned-proxmox-at-birth.nix])
    (choose [./modules/lix-default.nix ../lix-default.nix])
    (choose [./modules/secrets-config/sops-the-blank-system.nix ../secrets-config/sops-the-blank-system.nix])
    (choose [./modules/toolsets/grafana_metric.nix ../toolsets/grafana_metric.nix])
    (choose [./modules/secrets-config/sops-mail.nix ../secrets-config/sops-mail.nix])
  ];

  config = {
    # Create /etc/stalwart secret files so the generated TOML can reference them
    environment.etc = {
      "stalwart/mail-pw1".text = boardPassword; # principal password (board)
      "stalwart/mail-pw1".mode = "0777";
      "stalwart/mail-pw2".text = utilityPassword; # principal password (utility)
      "stalwart/mail-pw2".mode = "0777";
      "stalwart/admin-pw".text = adminPassword; # admin fallback password
      "stalwart/admin-pw".mode = "0777";
      "stalwart/acme-secret".text = cloudflareToken; # API token for ACME (Cloudflare)
      "stalwart/acme-secret".mode = "0777";
      "stalwart/cloudflare-username".text = cloudflareUsername; # contact email for ACME
      "stalwart/cloudflare-username".mode = "0777";
    };

    systemd.tmpfiles.rules = [
      # z = create/modify file or directory, set mode and owner
      "z /etc/stalwart 0555 root root - -"
    ];

    # Enable Tailscale for remote access to Traefik dashboard and configuration
    services.tailscale.enable = true;

    local.hostname = "nixos-mailserver";
    local.username = "mailprg";
    local.userDescription = "NixOS PRG Mailing Service";
    local.address = "10.1.1.15";
    system.stateVersion = "25.11";

    services.stalwart-mail = {
      enable = true;
      openFirewall = true;
      settings = {
        server = {
          hostname = "mail.prg-radio.org";
          tls = {
            enable = true;
            implicit = true;
          };
          listener = {
            smtp = {
              protocol = "smtp";
              # Use port 587 for SMTP submission with STARTTLS, as port 25 is often blocked by ISPs for outgoing mail to prevent spam.
              # This way, you can still receive mail on port 25 but require authenticated submission on port 587.
              bind = "[::]:25"; # I am so fucking fed up this shit, this fucking ISP is sending me to early grave.
            };
            submissions = {
              bind = "[::]:465";
              protocol = "smtp";
              tls.implicit = true;
            };
            imaps = {
              bind = "[::]:993";
              protocol = "imap";
              tls.implicit = true;
            };
            jmap = {
              bind = "[::]:8080";
              url = "https://mail.prg-radio.org";
              protocol = "http";
            };
            management = {
              bind = ["127.0.0.1:8080" "[::]:8081"];
              protocol = "http";
            };
          };
        };
        lookup.default = {
          hostname = "mail.prg-radio.org";
          domain = "prg-radio.org";
        };
        acme."letsencrypt" = {
          directory = "https://acme-v02.api.letsencrypt.org/directory";
          challenge = "dns-01";
          # reference the contact and secret via files under /etc/stalwart
          contact = "%{file:/etc/stalwart/cloudflare-username}%";
          domains = ["prg-radio.org" "mailadmin.prg-radio.org" "mail.prg-radio.org"];
          provider = "cloudflare";
          secret = "%{file:/etc/stalwart/acme-secret}%";
        };
        session.auth = {
          mechanisms = ["plain"];
          directory = "in-memory";
        };
        storage.directory = "in-memory";
        session.rcpt.directory = "in-memory";
        directory."imap".lookup.domains = ["prg-radio.org"];
        directory."in-memory" = {
          type = "memory";
          principals = [
            {
              class = "individual";
              name = "Polyteknisk Radiogruppe Board Member";
              secret = "%{file:/etc/stalwart/mail-pw1}%";
              email = ["board@prg-radio.org"];
            }
            {
              class = "individual";
              name = "postmaster";
              secret = "%{file:/etc/stalwart/mail-pw1}%";
              email = ["postmaster@prg-radio.org"];
            }
            {
              class = "individual";
              name = "no-reply";
              secret = "%{file:/etc/stalwart/mail-pw2}%";
              email = ["no-reply@prg-radio.org"];
            }
            {
              class = "individual";
              name = "service";
              secret = "%{file:/etc/stalwart/mail-pw2}%";
              email = ["service@prg-radio.org"];
            }
          ];
        };
        authentication.fallback-admin = {
          user = "admin";
          secret = "%{file:/etc/stalwart/admin-pw}%";
        };
      };
    };

    networking.firewall.allowedTCPPorts = [
      25
    ];
    networking.firewall.allowedUDPPorts = [
      25
    ];
  };
}