ASP.NET C＃ - 从Gmail / Yahoo Live SMTP Server发送电子邮件不起作用

Question

I am struggling with attempting to send email from a .NET application.

I have tried everything from making a new account both gmail and yahoo (changed the host for yahoo), as well as, changing the port using and not using mail.To, allowing less secure apps, i also tried enabling 2 step verification and giving an application password for gmail all of which have failed with the same caught error of: {"The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.7.1 Authentication required"}

This is my code:

 SmtpClient smtpClient = new SmtpClient();
        System.Net.NetworkCredential credentials = new System.Net.NetworkCredential("myemail@gmail.com", "pw");
        smtpClient.Credentials = credentials;
        smtpClient.UseDefaultCredentials = false;
        smtpClient.Port = 587;
        smtpClient.EnableSsl = true;
        smtpClient.Host = "smtp.gmail.com";
        smtpClient.DeliveryMethod = SmtpDeliveryMethod.Network;

        MailMessage mail = new MailMessage();
        mail.From = new MailAddress("myemail@gmail.com");
        mail.To.Add("myemail@gmail.com");
        mail.IsBodyHtml = true;
        mail.Subject = txtSubject.Text;
        mail.Body = txtBody.Text;
        try
        {
            smtpClient.Send(mail);
        }
        catch (Exception ex)
        {
            throw ex;
        }
        finally
        {
            if (mail != null)
            {
                mail.Dispose();
            }
        }

Solution: as people may have the problem in the future the solution was to remove the line of code: smtpClient.UseDefaultCredentials = false;

Answer 1

smtpClient.UseDefaultCredentials = false;            
System.Net.NetworkCredential credentials = new System.Net.NetworkCredential("myemail@gmail.com", "pw");
smtpClient.Credentials = credentials;

Use those lines in such order.