Unable to read data from the transport connection?

Question

This is my first post on Stack, and I've literally just started programming, so please, be patient.

I'm attempting to send an email to "x" email address when Button 1 is pressed. I've looked around, and every thread is jargon-heavy and not in my context. Please pardon me if this is a "newb' question, or if it's already thouroughly answered somewhere else.

The error I'm getting is " Failure sending mail. ---> System.IO.IOException: Unable to read data from the transport connection: net_io_connectionclosed."

Here's my code

 using (SmtpClient smtp = new SmtpClient())
        {
            smtp.Host = "smtp.gmail.com";
            smtp.Port = 465;
            smtp.Credentials = new NetworkCredential("myemail", "mypassword");
            string to = "toemail";
            string from = "myemail";
            MailMessage mail = new MailMessage(from, to);
            mail.Subject = "test test 123";
            mail.Body = "test test 123";
            try
            {
                smtp.Send(mail);
            }
            catch (Exception ex)
            {
                Console.WriteLine("Exception caught in CreateTestMessage2(): {0}",
                            ex.ToString());
            }

Any help is greatly appreciated!

Answer 1

The error you're getting could come from a plethora of things from a failed connection, to the server rejecting your attempts, to the port being blocked.

I am by no means an expert on SMTP and its workings, however, it would appear you are missing setting some of the properties of the SmtpClient.

I also found that using port 465 is a bit antiquated, and when I ran the code using port 587, it executed without an issue. Try changing your code to something similar to this:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Net.Mail;
using System.Net;

namespace EmailTest
{
    class Program
    {
        static void Main(string[] args)
        {
            SendMail();
        }

        public static void SendMail()
        {
            MailAddress ma_from = new MailAddress("senderEmail@email", "Name");
            MailAddress ma_to = new MailAddress("targetEmail@email", "Name");
            string s_password = "accountPassword";
            string s_subject = "Test";
            string s_body = "This is a Test";

            SmtpClient smtp = new SmtpClient
            {
                Host = "smtp.gmail.com",
                //change the port to prt 587. This seems to be the standard for Google smtp transmissions.
                Port = 587,
                //enable SSL to be true, otherwise it will get kicked back by the Google server.
                EnableSsl = true,
                //The following properties need set as well
                DeliveryMethod = SmtpDeliveryMethod.Network,
                UseDefaultCredentials = false,
                Credentials = new NetworkCredential(ma_from.Address, s_password)
            };


            using (MailMessage mail = new MailMessage(ma_from, ma_to)
            {
                Subject = s_subject,
                Body = s_body

            })

                try
                {
                    Console.WriteLine("Sending Mail");
                    smtp.Send(mail);
                    Console.WriteLine("Mail Sent");
                    Console.ReadLine();
                }
                catch (Exception ex)
                {
                    Console.WriteLine("Exception caught in CreateTestMessage2(): {0}",
                                ex.ToString());
                    Console.ReadLine();
                }

        }

    }
}

Tested to work as well. Also of note: if your Gmail account does not allow "Less Secure" apps to access it, you'll get an error and message sent to your inbox stating an unauthorized access attempt was caught.

To change those settings, go here.

Hope this helps, let me know how it works out.