services.postfix = {
    enable = true;
    origin = "xy.com";
    domain = "xy.com";
    hostname = "host.xy.com";

    extraConfig = ''
        milter_default_action = accept
        smtpd_milters = unix:/run/opendkim/opendkim.sock
        non_smtpd_milters = unix:/run/opendkim/opendkim.sock
    '';
  };