code: public static SmtpRequest rcpt(CharSequence recipient, CharSequence... rcptParameters) {
          ObjectUtil.checkNotNull(recipient, "recipient");
          if (rcptParameters == null || rcptParameters.length == 0) {
              return new DefaultSmtpRequest(SmtpCommand.RCPT, "TO:<" + recipient + '>');
          } else {
              List<CharSequence> params = new ArrayList<CharSequence>(rcptParameters.length + 1);
              params.add("TO:<" + recipient + '>');
              for (CharSequence param : rcptParameters) {
                  params.add(param);
              }
              return new DefaultSmtpRequest(SmtpCommand.RCPT, params);
          }
      }
docs: Creates a {@code RCPT} request.