Send Email over SSL/TLS in C#¶

In previous section, I introduced how to send email in a simple C# project. In this section, I will introduce how to send email over SSL/TLS connection in C#.

Sections:

SSL and TLS Introduction
TLS 1.2
[C# - Send Email over SSL/TLS Setting - Example]
[C# - Send Email over Implicit SSL on 465 port - Example]
[C# - Send Email over TLS (Explicit SSL) on 25 or 587 port - Example]
SMTP Setting for Gmail, Yahoo, Hotmail and Office 365

SSL and TLS Introduction¶

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

EASendMail SMTP component supports both ways. The connection can be specified by EASendMail.SmtpConnectType enumeration. Please see the following example code

TLS 1.2¶

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, and you got connection error with SSL/TLS connection, 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

[C# - Send Email over SSL/TLS Setting - Example]¶

The following example codes demonstrates how to set SSL/TLS connection.

// Send email by normal TCP/IP without SSL connection
SmtpServer oServer = new SmtpServer("localhost 25");
oServer.ConnectType = SmtpConnectType.ConnectNormal;

// Send email by SSL connection with STARTTLS command switching
SmtpServer oServer = new SmtpServer("localhost 25");
oServer.ConnectType = SmtpConnectType.ConnectSTARTTLS;

// Send email by SSL connection with direct SSL.
SmtpServer oServer = new SmtpServer("localhost 465");
oServer.ConnectType = SmtpConnectType.ConnectDirectSSL;

// Send email by SSL connection with auto-detect.
// If port is 25 or 587, STARTTLS SSL will be used; otherwise direct SSL will be used.
SmtpServer oServer = new SmtpServer("localhost 465");
oServer.ConnectType = SmtpConnectType.ConnectSSLAuto;

SmtpServer oServer = new SmtpServer("localhost 25");
oServer.ConnectType = SmtpConnectType.ConnectSSLAuto;

// If server supports SSL/TLS, then SSL/TLS is used, otherwise normal TCP is used.
SmtpServer oServer = new SmtpServer("localhost 25");
oServer.ConnectType = SmtpConnectType.ConnectTryTLS;

SmtpServer oServer = new SmtpServer("localhost 587");
oServer.ConnectType = SmtpConnectType.ConnectTryTLS;

Note

Remarks: All of samples in this section are based on first section: Send email in a simple C# project. To compile and run the following example codes successfully, please click here to learn how to create the test project and add reference of EASendMail to your project.

[C# - Send Email over Implicit SSL on 465 port - Example]¶

The following example codes demonstrate how to send email over SSL connection on 465 port.

Note

To get the full sample projects, please refer to Samples section.

using System;
using System.Collections.Generic;
using System.Text;
using EASendMail; //add EASendMail namespace

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

                oMail.From = "test@emailarchitect.net";
                oMail.To = "support@emailarchitect.net";

                oMail.Subject = "test email from c# project";
                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
                oServer.User = "test@emailarchitect.net";
                oServer.Password = "testpassword";

                // Set SSL 465 port
                oServer.Port = 465;
                // Set direct SSL connection, you can also use ConnectSSLAuto
                oServer.ConnectType = SmtpConnectType.ConnectDirectSSL;

                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);
            }
        }
    }
}

[C# - Send Email over TLS (Explicit SSL) on 25 or 587 port - Example]¶

The following example codes demonstrate how to send email over TLS (STARTTLS command, Explicit SSL) connection on 25 port.

Note

To get the full sample projects, please refer to Samples section.

using System;
using System.Collections.Generic;
using System.Text;
using EASendMail; //add EASendMail namespace

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

                oMail.From = "test@emailarchitect.net";
                oMail.To = "support@emailarchitect.net";

                oMail.Subject = "test email from c# project";
                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
                oServer.User = "test@emailarchitect.net";
                oServer.Password = "testpassword";

                // Set 25 port, if your server uses 587 port, please change 25 to 587
                oServer.Port = 25;
                // Set TLS connection, you can also use ConnectSSLAuto
                oServer.ConnectType = SmtpConnectType.ConnectSTARTTLS;

                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);
            }
        }
    }
}

SMTP Server SSL Certificate

To send email over SSL/TLS connection, you don’t need to install a certificate on your machine. The data is encrypted by server certificate public/private key pair.

SMTP Setting for Gmail, Yahoo, Hotmail and Office 365¶

Because most popluar email providers support or require SSL/TLS connection, so I will introduce specific setting for Gmail, Yahoo, Hotmail and Office 365 in the coming sections.

Next Section

At next section I will introduce how to send email using Gmail account in C#.

Tutorial Index

Send Email over SSL/TLS in C#¶

SSL and TLS Introduction¶

TLS 1.2¶

[C# - Send Email over SSL/TLS Setting - Example]¶

[C# - Send Email over Implicit SSL on 465 port - Example]¶

[C# - Send Email over TLS (Explicit SSL) on 25 or 587 port - Example]¶

SMTP Setting for Gmail, Yahoo, Hotmail and Office 365¶

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