Authentication error sending SMTP Request

Question

i'm writing a C# email application which is currently being designed for use with Gmail so I can test authentication. However I'm getting an error which doesn't seem to make much sense as I am setting SSL to true and using a user and password.

Error Message: System.Net.Mail.SmtpException: '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'

using System;
using System.Net;
using System.Net.Mail;

namespace EmailSendingProgram
{
    public class EmailSendingClass
    {
        public static void Main(string[] args)
        {
            Console.WriteLine("Type your Gmail Address: ");
            string from = Console.ReadLine();

            Console.WriteLine("Type your Gmail Password: ");
            string password = Console.ReadLine();

            Console.WriteLine("Type the Email Address you wish to send to: ");
            string to = Console.ReadLine();

            Console.WriteLine("Type the Subject of the email: ");
            string subject = Console.ReadLine();

            Console.WriteLine("Type or paste in your email (either text or HTML): ");
            string body = Console.ReadLine();

            EmailSendingClass email = new EmailSendingClass();
            email.Send(from, password, to, subject, body);
        }

        /// handles sending the email
        /// hardcoded to work with gmail just change the CreateSmtpClient from 
        /// "smtp.gmail.com", 587 to whatever you want to use
        public void Send(string from, string password, string to, string subject, string body)
        { 
            var message = CreateMailMessage(from, to, subject, body);

            // Host and Port setup for use with Gmail
            using (SmtpClient client = CreateSmtpClient("smtp.gmail.com", 587, from, password))
            {
                client.Send(message);
            }
        }

        /// Defines the SmtpClient for the mail message 
        /// setups up the network credentials to send the email
        private SmtpClient CreateSmtpClient(string host, int port, string from, string password)
        {
            SmtpClient client = null;

            client = new SmtpClient()
            {
                Host = host,
                Port = port,
                EnableSsl = true,
                Credentials = new NetworkCredential(from, password)
            };

            return client;
        }

        /// defines what is contained in the email and where it will be sent
        /// also makes all messages send as HTML
        private MailMessage CreateMailMessage(string from, string to, string subject, string body)
        {
            MailMessage message = null;

            message = new MailMessage(from, to)
            {
                Subject = subject,
                Body = body
            };

            message.IsBodyHtml = true;
            return message;
        }
    }
}

I understand that something is being done incorrectly with the authentication but I can't seem to figure out what specifically. So any help would be appreciated.

Answer 1

The issue wasn't the program but rather was Gmail refusing sign in from "less secure apps"

I simply clicked the secure your account button and allowed this account to be signed in from less secure apps.