code: public static SmtpRequest mail(CharSequence sender, CharSequence... mailParameters) {
          if (mailParameters == null || mailParameters.length == 0) {
              return new DefaultSmtpRequest(SmtpCommand.MAIL,
                                            sender != null ? "FROM:<" + sender + '>' : FROM_NULL_SENDER);
          } else {
              List<CharSequence> params = new ArrayList<CharSequence>(mailParameters.length + 1);
              params.add(sender != null? "FROM:<" + sender + '>' : FROM_NULL_SENDER);
              for (CharSequence param : mailParameters) {
                  params.add(param);
              }
              return new DefaultSmtpRequest(SmtpCommand.MAIL, params);
          }
      }
docs: Creates a {@code MAIL} request.