Unable to send email programmatically

Question

The code below is throwing an exception:

The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.5.1 Authentication Required. Learn more at

var fromAddress = new MailAddress(toEmail, "From Name");
var toAddress = new MailAddress(fromEmail, "To Name");
const string fromPassword = "******";
string subject = sub;
try
{
var smtp = new SmtpClient
  {
     Host = "smtp.gmail.com",
     Port = 587,
     EnableSsl = true,
     DeliveryMethod = SmtpDeliveryMethod.Network,
     UseDefaultCredentials = false,
     Credentials = new NetworkCredential(fromAddress.Address, fromPassword)            };
     using (var message = new MailMessage(fromAddress, toAddress)
     {
        Subject = subject,
        Body = body
      })
     {
       smtp.Send(message);
     }
 }
 catch (Exception ex)
 {
   Console.WriteLine(ex.Message);
 }