code: public void forcedlyDirect(String subject, String plainBody) {
          postcard.useDirectBody(plainBody).useWholeFixedText().forcedlyDirect(subject);
      }
docs: Set subject and plain body as forcedly-direct. <br>
  It ignores body file settings. (conversely can keep them)
  @param subject The subject to be sent plainly. (NotNull)
  @param plainBody The plain body to be sent plainly. (NotNull)