Sending an email with html-body content

I’ m trying to sent a mail with a html-body like this. But the html is not recognised in the emailclient. Should i append ‘isHtml => true’ or something like that somewhere? Like you should do in phpMailer?

  'from'    => '',
  'to'      => $contactEmail,
  'subject' => $subject,
  'body'    => $htmlTxt

Could you please state what Kirbz version zou are using? (Or select the appropriate category for your post)

ok, it works now! thanks!