Sending mail with HTML and Attachments

Question

Hi there.

At work we want to create a email applicaion that send a HTML / Plain Text Message but with or without a attachment... We created it in a windows forms application.  If you send a normal HTML / Text Mail using outlook... the server auto generate a disclaimer at the botom of the message everytime.  the problem begins with...

1.   When we send a mail without an attachment... the HTML / Text message message display correct with the disclaimer.
2.   When we send a mail with an attachment... the HTML / Text message do not display at all... also with the disclaimer.

Here follow the code we have...

 try
                {
                    from = "\"Lithotech Account in C# Application\" <" + txtFrom.Text + ">";
                    to = txtTo.Text;
                    user = txtTo.Text;
                    subject = txtSubject.Text;
                    message = txtMessage.Text;
                    SmtpClient client = new SmtpClient("155.236.11.143", 25);
                    client.Credentials = new NetworkCredential(username, password);
                    client.EnableSsl = false;
                    StringBuilder mailBody = new StringBuilder(".");
                    int n = user.IndexOf("@");
                    if (n != -1)
                    {
                        mailBody.AppendLine("<h1>Dear " + user.Substring(0, n) + "</h1>");
                    }
                    mailBody.AppendLine("<br />");
                    mailBody.AppendLine("<p>" + message + "</p>");
                    MailMessage msg = new MailMessage(from, to, subject, mailBody.ToString());
                    msg.IsBodyHtml = true;
                    DialogResult attachment = MessageBox.Show("Do you want to add any attachments?", "Attachments", MessageBoxButtons.YesNo, MessageBoxIcon.Question);
                    if (attachment == DialogResult.Yes)
                    {
                        Cursor.Current = Cursors.WaitCursor;
                        OpenFileDialog file = new OpenFileDialog();
                        file.Filter = "Text Files (*.txt)|*.txt|C Sharp Files (*.cs)|*.cs";
                        file.Title = "Add attachments";

                        if (file.ShowDialog() == DialogResult.Cancel)
                            return;
                        FileStream fstream;
                        try
                        {
                            fstream = new FileStream(file.FileName, FileMode.Open, FileAccess.Read);
                            StreamReader reader = new StreamReader(fstream);
                            while (reader.Peek() >= 0)
                            {
                                string str = reader.ReadLine();
                                richTextBox1.Text += str + '\n';
                            }
                            Attachment attatchment = new Attachment(file.FileName);
                            msg.Attachments.Add(attatchment);
                            string AttFileName = new System.IO.FileInfo(@file.FileName).Name;
                            MessageBox.Show(AttFileName + " as Attachment added", "Success", MessageBoxButtons.OK, MessageBoxIcon.Information);
                            Cursor.Current = Cursors.WaitCursor;
                            client.Send(msg);
                            Cursor.Current = Cursors.WaitCursor;
                            MessageBox.Show("Message and attachment sent successfully!", "Sent Message", MessageBoxButtons.OK, MessageBoxIcon.Information);
                            Cursor.Current = Cursors.Default;
                            txtTo.Clear();
                            txtSubject.Clear();
                            txtMessage.Clear();
                            txtTo.Focus();
                        }
                        catch (Exception)
                        {
                            MessageBox.Show("Error opening file", "File Error",
                                             MessageBoxButtons.OK, MessageBoxIcon.Exclamation);
                        }
                    }
                    else if (attachment == DialogResult.No)
                    {
                        Cursor.Current = Cursors.WaitCursor;
                        client.Send(msg);
                        MessageBox.Show("Message sent successfully!", "Sent Message", MessageBoxButtons.OK, MessageBoxIcon.Information);
                        Cursor.Current = Cursors.Default;
                        txtTo.Clear();
                        txtSubject.Clear();
                        txtMessage.Clear();
                        txtTo.Focus();
                    }
                }
                catch (Exception ex)
                {
                    MessageBox.Show("Unable to send message due to the following reason: " + '\n' + ex.Message);
                }
            }