Question

It works great to send emails (to Outlook) in HTML format by assigning the text/html content type string like so:

using (MailMessage message = new MailMessage())
{
  message.From = new MailAddress("[e-mail]");
  message.ReplyTo = new MailAddress("[e-mail]");
  message.To.Add(new MailAddress("[e-mail]"));
  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);
  }
}

The email is correctly recognized as HTML in Outlook (2003).
But if I try rich text:

MediaTypeNames.RichText;

Outlook doesn’t detect this, it falls back to plain text.
How do I send email in rich text format?

Answer 1

The bottom line is, you can’t do this easily using System.Net.Mail.

The rich text in Outlook is sent as a winmail.dat file in the SMTP world (outside of Exchange).

The winmail.dat file is a TNEF message. So, you would need to create your richtext inside of the winmail.dat file (formatted to TNEF rules).

However, that’s not all. Outlook uses a special version of compressed RTF, so, you would also need to compress your RTF down, before it’s added to the winmail.dat file.

The bottom line, is this is difficult to do, and unless the client really, really needs this functionality, I would rethink it.

This isn’t something you can do with a few lines of code in .NET.