c# – 如何以富文本格式向Outlook发送电子邮件？

using (MailMessage message = new MailMessage())
{
  message.From = new MailAddress("--@---.com");
  message.ReplyTo = new MailAddress("--@---.com");
  message.To.Add(new MailAddress("---@---.com"));
  message.Subject = "This subject";
  message.Body = "This content is in plain text";
  message.IsBodyHtml = false;

  string bodyHtml = "<p>This is the HTML <strong>content</strong>.</p>";

  using (AlternateView altView = AlternateView.CreateAlternateViewFromString(bodyHtml,new ContentType(MediaTypeNames.Text.Html)))
  {
    message.AlternateViews.Add(altView);
    SmtpClient smtp = new SmtpClient(smtpAddress);
    smtp.Send(message);
  }
}

电子邮件在Outlook(2003)中被正确识别为HTML.
但如果我尝试富文本：

MediaTypeNames.RichText;

Outlook没有检测到这一点,它回退到纯文本.
如何以富文本格式发送电子邮件？