code: @PostMapping
    public String submitFeedback(@Valid FeedbackForm form) {
      if (appSettings.getRecaptchaIsEnabled() && !reCaptchaService.validate(form.getRecaptcha())) {
        form.setErrorMessage(
            messageSource.getMessage("feedback_recaptcha_validation_failed", null, getLocale()));
        return VIEW_FEEDBACK;
      }
      try {
        LOG.info("Sending feedback:{}", form);
        SimpleMailMessage message = createFeedbackMessage(form);
        mailSender.send(message);
        form.setSubmitted(true);
      } catch (MailAuthenticationException e) {
        LOG.error("Error authenticating with email server.", e);
        form.setErrorMessage(
            messageSource.getMessage("feedback_not_authenticated_mail_server", null, getLocale()));
      } catch (MailSendException e) {
        LOG.error("Error sending mail", e);
        form.setErrorMessage(
            messageSource.getMessage("feedback_not_authenticated_mail_server", null, getLocale()));
      }
      return VIEW_FEEDBACK;
    }
docs: Handles feedback form submission.