Web Forms :: Sending Mail As Typed From A Multiline Textbox?

I know how to send mail from a form.But what i want to know is this.

I have a multiline textbox to type the message.I typed a line of text and pressed the Enter key to go to the next line and so on i entered many lines of text.But when i view the message , what i am seeing is a continous line of text wihtout seeing the text line by line as i typed in the textbox.how can i make it view as i typed ie, first line in a line ,second line in another line and so on

My code is;

MailMessage message = new MailMessage();
message.From = new MailAddress(TextBox1.Text);
message.To.Add(new MailAddress(TextBox2.Text));
message.IsBodyHtml = true;
message.Subject = TextBox3.Text;
message.Body = TextBox4.Text;
message.Priority = MailPriority.Normal;
SmtpClient mSmtpClient = new SmtpClient();
mSmtpClient.Send(message);