Send Email in C# - Tutorial¶

Send Email in A Simple C# Project using SMTP protocol¶

To better demonstrate how to send email in C# using SMTP protocol, let’s create a C# console project named “mysendmail” at first, and then add the reference of EASendMail in your project.

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 and go to menu -> Project -> Add Reference -> .NET -> Browse..., and select the Installation Path\Lib\net[version]\EASendMail.dll from local disk, click Open -> OK, the reference will be added to the project, and you can start to use it to send email in the project.

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");

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

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

                // User and password for ESMTP authentication
                oServer.User = "test@emailarchitect.net";
                oServer.Password = "testpassword";

                // Most mordern SMTP servers require SSL/TLS connection now.
                // ConnectTryTLS means if server supports SSL/TLS, SSL/TLS will be used automatically.
                oServer.ConnectType = SmtpConnectType.ConnectTryTLS;

                // If your SMTP server uses 587 port
                // oServer.Port = 587;

                // If your SMTP server requires SSL/TLS connection on 25/587/465 port
                // oServer.Port = 25; // 25 or 587 or 465
                // 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);
            }
        }
    }
}

Common SMTP Transport Error¶

When you execute above example code, if it threw an exception about “Networking connection” or “No such host”, it is likely that your SMTP server address is not correct. If it threw an exception about “5xx Relay denied”, it is likely that you did not set user authentication. Another common error is “5xx Must issue a STARTTLS command first” or “No supported authentication marshal found!”, that is because your SMTP server requires user authentication under SSL connection. You can set the SSL connection to solve this problem. You can learn more detail in Troubleshooting section.

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

Where can I get my SMTP email server address, user and password?¶

Because each email account provider has different server address, so you should query your SMTP server address from your email account provider. To prevent spreading email from the server, most SMTP servers also require user authentication. User name is your email address or your email address without domain part, it depends on your email provider setting.

Finally, if you have already set your account in your email client such as Outlook or Window Mail, you can query your SMTP server address, user in your email client. For example, you can choose menu -> “Tools” - > - “Accounts” - > “Your email account” - > “Properties” - > “Servers” in Outlook express or Windows Mail to get your SMTP server, user. Using EASendMail to send email does not require you have email client installed on your machine or MAPI, however you can query your exist email accounts in your email client.

Email Address Syntax and Multiple Recipients¶

The following example codes demonstrates how to specify display name and email address by different syntax.

// For single email address (From, ReplyTo, ReturnPath), the syntax can be:
// ["][display name]["]<email address>

// For example:
"Tester, T" <test@adminsystem.com>
Tester <test@adminsystem.com>
<test@adminsystem.com>
test@adminsystem.com

// For mulitple email address (To, CC, Bcc), the syntax can be:
// [single email],[single email]...
// (,;\r\n) can be used to separate multiple email addresses.

// For example:
"Tester, T" <test1@adminsystem.com>, Tester2 <test2@adminsystem.com>,
    <test3@adminsystem.com>, test4@adminsystem.com

[C# - Email Address Syntax - Example]

To better understand the email address syntax, please refer to the following codes. It demonstrate how to specify from, to, cc by different email address syntax.

// From is a MailAddress object, it supports implicit converting from string.
// The syntax is like this: "test@adminsystem.com" or "Tester<test@adminsystem.com>"
// The example code without implicit converting:
oMail.From = new MailAddress( "Tester", "test@adminsystem.com" );
oMail.From = new MailAddress( "Tester<test@adminsystem.com>");
oMail.From = new MailAddress( "test@adminsystem.com" );

// To, Cc and Bcc is a AddressCollection object, it supports implicit converting
// from string. Multiple addresses are separated with (,;)
// The syntax is like this: "test@adminsystem.com, test1@adminsystem.com"
// The example code without implicit converting:
oMail.To = new AddressCollection( "test1@adminsystem.com, test2@adminsystem.com" );
oMail.To = new AddressCollection( "Test1<test@adminsystem.com>, Test2<test2@adminsystem.com>");
// You can add more recipient by Add method:
oMail.To.Add( new MailAddress( "tester", "test@adminsystem.com"));

// You can also add carbon copy (CC) or blind carbon copy (BCC) in the email:
oMail.Cc.Add( new MailAddress( "CC recipient", "cc@adminsystem.com"));
oMail.Bcc.Add( new MailAddress( "Bcc recipient", "bcc@adminsystem.com"));

From, ReplyTo, Sender and Return-Path¶

From, Reply-To, Sender and Return-Path are common email headers in email message. You should always set From property at first, it is a MUST to identify the email sender. The following table lists the header and corresponding properties:

• From

  This property indicates the original email sender. This is what you see as the “FROM” in most mail clients.

• Reply-To

  This property indicates the reply address. Basically, when the user clicks “reply” in mail client, the Reply-To value should be used as the recpient address of the replied email. If you don’t set this property, the Reply address is same as From address.

• Sender

  This property indicates the who submit/send the email. When the user received the email, the email client displays: From: “sender address” on behalf of “from address”. If you don’t set this property, the Sender address is same as From address. Sender property is common used by mail listing provider. This property also takes effect to DKIM/DomainKeys signature, if Sender is different with From address, then you should sign DKIM/DomainKeys based on Sender domain instead of From address domain.

• Return-Path

  This property indicates the delivery notification report address. If you don’t set this property, the Return-Path address is same as From address. This property also takes effect to SPF record, if Return-Path is different with From address, then remote SMTP server checkes SPF record of Return-Path instead of From address.

[C# - From, ReplyTo, Sender and Return-Path in Email - Example]

The following example codes demonstrate how to specify From, Reply-To, Sender and Return-Path in Email. With the following example codes:

• If the email couldn’t be delivered to recipient, a non-delivery report will be sent to report@emailarchitect.net.
• If the user received the email, the email client will display: sender@emailarchitect.net on behalf of from@adminsystem.com.
• If the user click “reply”, the replied email will be sent to reply@adminsystem.com.

SmtpMail oMail = new SmtpMail("TryIt");
oMail.From = "from@adminsystem.com";
oMail.ReplyTo = "reply@adminsystem.com";
oMail.Sender = "sender@emailarchitect.net";
oMail.ReturnPath = "report@emailarchitect.net";

Mail Priority¶

If you want to set Higher or Lower priority to your email, you can use Priority prority

[C# - Mail Priority - Example]

// Set high priority
oMail.Priority = MailPriority.High;

Troubleshooting¶

When you send email in above simple C# project, if it threw an exception, please have a look at the following tips:

Using Telnet to detect networking connection to SMTP server¶

Note

Notice: in Windows 2008/Windows 8 or later version, Telnet Client is not installed by default, you should enable this command in Control Panel -> Programs and Features -> Turn Windows feature on or off -> have Telnet Client checked.

Under DOS command prompt, input “telnet [serveraddress] [port]”:

telnet mail.emailarchitect.net 25
press enter.

If the networking connection to your SMTP server is good, it should return a message like 220 .... If it returns Could not open connection to ..., that means the networking connection to SMTP server is bad, or outbound 25 port is blocked by anti-virus software, firewall or ISP. Please have a look at the following screenshot:

// If your smtp server requires TLS connection, please add this line
oServer.ConnectType = SmtpConnectType.ConnectSSLAuto;

try
{
    // add this line here to generate log file
    oSmtp.LogFileName = "d:\\smtp.txt";
    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);
}

Process Bounced Email (Non-Delivery Report)¶

If you sent email successfully without error, that means the email has been submitted to the SMTP server. The SMTP server will deliver the email in background, if the email couldn’t be delivered, a Failure Report (NDS) will be sent back to your sender email address.

To retrieve and parse Failure Report (NDS), you should monitor your sender mailbox. I recommend that you use EAGetMail to monitor your sender mailbox using POP3/IMAP4/Exchange WebDAV/Exchange Web Service protocol. After you installed EAGetMail on your machine, there are several full samples named “parse_report.*” for VB.NET, C# in the installation path.

Email Tracking¶

Email tracking is used to verify that emails are actually read by recipients. There are two common solutions: Read Receipt and Linked Image Tracking

To learn more detail about Process Bounced Email (Non-Delivery Report) and Email Tracking, please have a look at this topic: Process Bounced Email (Non-Delivery Report) and Email Tracking

Bulk Email Sender Guidelines¶

If you are a mail listing provider and send bulk emails every day, of course you don’t want your emails are blocked or moved to Junk folder of the recipient mailbox.

To increase the inbox delivery rate of your messages, make sure that all recipients on your distribution lists actually want to receive the mail. Have a look the topic for some tips on how to make sure your messages are welcomed by most email providers:

Bulk Email Sender Guidelines

Next Section

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