I also have this problem when I wanna send an email using SMTP method this is my code:

MailMessage message = new MailMessage("my-email-address", "target-address");
                message.Body = "*****";
                message.Subject = "Hello";
                var client = new SmtpClient("smtp.gmail.com");
                client.Port = 587;
                client.Credentials = new NetworkCredential("amin h", "***");
                client.EnableSsl = true;
                client.Send(message);

can anyone help me?