จะเขียนดักยังไงให้ไม่มีไฟล์ใน attachment ก็ส่งemailเป็นข้อความธรรมดาไปได้ครับ

                MailMessage mail = new MailMessage();
                //SmtpClient smtpServer = new SmtpClient("imap.inetmail.cloud");
                SmtpClient smtpServer = new SmtpClient("smtp.gmail.com");
                mail.From = new MailAddress(textBox1.Text);
                mail.To.Add(textBox3.Text);
                mail.Subject = textBox5.Text;
                mail.Body = textBox4.Text;
                mail.Attachments.Add(new Attachment(textBox6.Text));
                smtpServer.Port = 587;
                smtpServer.Credentials = new System.Net.NetworkCredential(textBox1.Text, textBox2.Text);
                smtpServer.EnableSsl = true;
                smtpServer.Send(mail);
                mail = null;
                MessageBox.Show("Mail Send Success Fully");