C# - Send email over TLS on 25 or 587 port¶

SSL and TLS¶

SSL connection encrypts data between the SMTP component and SMTP server to protects user, password and email content in TCP/IP level. Now this technology is commonly used and many SMTP servers are deployed with SSL such as Gmail, Yahoo and Hotmail. There are two ways to deploy SSL on SMTP server:

• Explicit SSL (TLS)

  Using STARTTLS command to switch SSL channel on normal SMTP port (25 or 587);

• Implicit SSL

  Deploying SSL on another port (465 or other port, you may query it from your server administrator

TLS 1.2 protocol¶

TLS is the successor of SSL, more and more SMTP servers require TLS 1.2 encryption now.

If your operating system is Windows XP/Vista/Windows 7/Windows 2003/2008/2008 R2/2012/2012 R2, you need to enable TLS 1.2 protocol in your operating system like this:

Enable TLS 1.2 on Windows XP/Vista/7/10/Windows 2008/2008 R2/2012

Installation¶

Before you can use the following codes, please download EASendMail SMTP Component and install it on your machine at first. Full sample proejcts are included in this installer.

Install from NuGet

You can also install the run-time assembly by NuGet. Run the following command in the NuGet Package Manager Console:

Install-Package EASendMail

Add reference¶

To use EASendMail SMTP Component in your project, the first step is Add reference of EASendMail to your project. Please create or open your project with Visual Studio, then go to menu -> Project -> Add Reference -> .NET -> Browse..., and select Installation Path\Lib\net[version]\EASendMail.dll from your disk, click Open -> OK, the reference of EASendMail will be added to your project, and you can start to use it to send email in your project.

.NET assembly¶

Because EASendMail has separate builds for .Net Framework, please refer to the following table and choose the correct dll.

Separate builds of run-time assembly for .NET Framework 2.0, 3.5, 4.0, 4.5, 4.6.1, 4.7.2, 4.8.1, .NET 5.0, .NET 6.0, .NET 7.0, .NET 8.0, .NET Standard 2.0 and .NET Compact Framework 2.0, 3.5.

C# - Send email over TLS on 25 or 587 port - example¶

The following example codes demonstrate how to send email over TLS connection on 25 or 587 port. In order to run it correctly, please change SMTP server, user, password, sender, recipient value to yours.

using System;
using System.Collections.Generic;
using System.Text;

// Add EASendMail namespace
using EASendMail;

namespace mysendemail
{
    class Program
    {
        static void Main(string[] args)
        {
            try
            {
                SmtpMail oMail = new SmtpMail("TryIt");

                // Set sender email address, please change it to yours
                oMail.From = "test@emailarchitect.net";

                // Set recipient email address, please change it to yours
                oMail.To = "support@emailarchitect.net";

                // Set email subject
                oMail.Subject = "test email from c#, tls 25 port";

                // Set email body
                oMail.TextBody = "this is a test email sent from c# project, do not reply";

                // Your SMTP server address
                SmtpServer oServer = new SmtpServer("smtp.emailarchitect.net");

                // User and password for ESMTP authentication, if your server doesn't require
                // User authentication, please remove the following codes.
                oServer.User = "test@emailarchitect.net";
                oServer.Password = "testpassword";

                // Set 25 or 587 port.
                oServer.Port = 25;

                // detect TLS connection automatically
                oServer.ConnectType = SmtpConnectType.ConnectSSLAuto;

                Console.WriteLine("start to send email ...");

                SmtpClient oSmtp = new SmtpClient();
                oSmtp.SendMail(oServer, oMail);

                Console.WriteLine("email was sent successfully!");
            }
            catch (Exception ep)
            {
                Console.WriteLine("failed to send email with the following error:");
                Console.WriteLine(ep.Message);
            }
        }
    }
}