The SMTP server requires a secure connection or the client was not authenticated. ….

Hello

I wrote this code. I searched but could not find a solution for my problem.

        private void button_sendemail_Click(object sender, EventArgs e)
        {
            string temp = "mygmailpassword";
            System.Security.SecureString password = new System.Security.SecureString();
            temp.ToCharArray().ToList().ForEach(p => password.AppendChar(p));
            string mailfrom = "…@gmail.com";
            string mailto = "…@yahoo.com";
            string subject = "Hello";
            string body = "Hello, I'm just writing this to say Hi!";
            using (MailMessage mail = new MailMessage())
            {
                mail.From = new MailAddress(mailfrom);
                mail.To.Add(mailto);
                mail.Subject = subject;
                mail.Body = body;
                mail.IsBodyHtml = true;
                // Can set to false, if you are sending pure text.
                using (SmtpClient smtp = new SmtpClient("smtp.gmail.com", 587))
                {
                    smtp.UseDefaultCredentials = false;
                    smtp.DeliveryMethod = SmtpDeliveryMethod.Network;
                    smtp.Credentials = new NetworkCredential(mailfrom, password);
                    smtp.EnableSsl = true;
                    smtp.Send(mail);
                }
            }
        }