services.postfix = {
    enable = true;
    ...
    extraConfig = ''
      smtp_sasl_auth_enable = yes
      smtp_sasl_password_maps = texthash:${config.age.secrets."postfix-sasl_passwd.age".path}
      local_header_rewrite_clients = static:all
      append_dot_mydomain = yes
    '';
    ...
  };