anchor.diff:          type = types.bool;
           default = false;
           description = "Whether to enable the OpenSMTPD server.";
  +      };
  +
  +      package = mkOption {
  +        type = types.package;
  +        default = pkgs.opensmtpd;
  +        defaultText = "pkgs.opensmtpd";
  +        description = "The OpenSMTPD package to use.";
         };
   
         addSendmailToSystemPath = mkOption {
  
positive.code:         chown smtpq.root /var/spool/smtpd/purge
          chmod 700 /var/spool/smtpd/purge
        '';
        serviceConfig.ExecStart = "${pkgs.opensmtpd}/sbin/smtpd -d -f ${conf} ${args}";
        environment.OPENSMTPD_PROC_PATH = "${procEnv}/libexec/opensmtpd";
      };
  
  
negative.code: 
    sendmail = pkgs.runCommand "opensmtpd-sendmail" {} ''
      mkdir -p $out/bin
      ln -s ${cfg.package}/sbin/smtpctl $out/bin/sendmail
    '';
  
  in {
  