I am using JavaMailSender with Spring Boot. I have a mail template, which has title and content. The content has /n or /t characters. But this does not effect on template. Mails are being received like those characters are not even exist. How can I apply these characters to the template?

My template: (.ftlh ):

<#import "mail-template.ftlh" as layout>

  <@layout.emailLayout title="Announcement" mailImage="image" clientBaseUrl="${frontendUrl}"; section>
   <#if section = "mailBody">
      <title>Announcent</title>
      Dear <strong>${name}</strong>,<br/>
      <strong>${title}</strong>
      <br/><br/>
      <strong>${content}</strong>
      <br/><br/> </#if>
  </@layout.emailLayout>

MailSender method:

@Async
    @Override
    public void sendMail(EmailData mail) throws MessagingException, TemplateException, IOException {
        var to = mail.getTo();
        var template = mail.getTemplate();
        var model = getModelWithFooterParam(mail.getModel());
        var mimeMessage = javaMailSender.createMimeMessage();
        var mailSubject = messageService.getMessage(template.getMailSubjectCode(), mail.getLocale());

        // init helper
        var helper = new MimeMessageHelper(mimeMessage, MimeMessageHelper.MULTIPART_MODE_MIXED_RELATED, "UTF-8");
        helper.setSubject(mailSubject);
        helper.setTo(to);
        helper.setFrom(from, displayName);
        String emailContent = getEmailContent(template.toString(), model);
        helper.setText(emailContent, true);

        // send mime message
        javaMailSender.send(mimeMessage);

    }

    private String getEmailContent(String templateFile, Map<String, Object> model) throws IOException,
            TemplateException {
        StringWriter stringWriter = new StringWriter();
        var template = configuration.getTemplate(templateFile);
        template.process(model, stringWriter);

        return stringWriter.getBuffer().toString();
    }

    private Map<String, Object> getModelWithFooterParam(Map<String, Object> model){
        var result = new HashMap<String, Object>();
        if (model != null) {
            result.putAll(model);
        }
        result.put(MailModelKeys.FOOTER_PROPS, mailFooterProps);
        result.put(MailModelKeys.FRONTEND_URL, frontendBaseUrl);
        return result;
    }

the title and the content are in the model map.

thanks.