Why Isn't My .NET Gmail SMTP Email Sending Code Working?

Troubleshooting .NET Gmail SMTP Email Sending Issues

Many developers encounter problems sending emails via Gmail's SMTP server using .NET. This guide provides solutions and working code examples.

Common Error: "The SMTP server requires a secure connection or the client was not authenticated."

This error indicates that your Gmail SMTP server requires authentication and a secure connection.

Working Code Example:

This C# code snippet demonstrates successful email sending through Gmail's SMTP server:

<code class="language-csharp">using System;
using System.Net;
using System.Net.Mail;

namespace EmailSender
{
    class Program
    {
        static void Main(string[] args)
        {
            // Configure SMTP client
            var client = new SmtpClient("smtp.gmail.com", 587)
            {
                Credentials = new NetworkCredential("[your_email@gmail.com]", "[your_password]"),
                EnableSsl = true
            };

            // Create email message
            var message = new MailMessage
            {
                From = new MailAddress("[your_email@gmail.com]"),
                To = { new MailAddress("[recipient_email@example.com]") },
                Subject = "Test Email",
                Body = "Test email body"
            };

            // Send email
            try
            {
                client.Send(message);
                Console.WriteLine("Email sent successfully!");
            }
            catch (Exception ex)
            {
                Console.WriteLine($"Error sending email: {ex.Message}");
            }

            Console.ReadLine();
        }
    }
}</code>

Important Note (2021 and Beyond):

For this code to function correctly, you must enable "less secure apps" access in your Gmail security settings. This setting can be found at https://www.php.cn/link/380714d486fbd50c0c9dfc7e4d8be9f7. This step is crucial to prevent authentication errors like "5.5.1 Authentication Required". Consider using App Passwords for enhanced security instead of your regular password.

Remember to replace placeholders like [your_email@gmail.com], [your_password], and [recipient_email@example.com] with your actual credentials and recipient's email address. If you continue to experience issues, double-check your Gmail settings and ensure that your firewall isn't blocking outgoing SMTP connections.

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