Email action ignores value of content_type attribute when attachment attribute is set

if(contentType.equals("text/html")) {
                MimeBodyPart bodyHtmlPart = new MimeBodyPart();
                bodyHtmlPart.setContent(body, contentType);
                multipart.addBodyPart(bodyHtmlPart);
            }
            else{
                MimeBodyPart bodyTextPart = new MimeBodyPart();
                bodyTextPart.setText(body);
                multipart.addBodyPart(bodyTextPart);
            }