Text message not sent?

Simple app, the sentMessage.TextBody has a string, but sentMessage.HtmlBody is empty. After sending the email. I got it in my outlook with only subject line. message body is missing. How do I send a plain text email?

smtp = new SmtpClient(…);
MailMessage sentMessage = some pre-assigned value.
smtp.Send(sentMessage);

Thx

If you want to send text body only, please don't set the HtmlBody property.