EASendMail SMTP Component > Developer Center > C# - .NET Framework > Send Email in C# - Tutorial

Send Email in C# - Tutorial

Date: June 26, 2014

Introduction

This tutorial introduces how to send email in C# using SMTP. It also demonstrates SSL, S/MIME, Embedded Images, Email Queue, Multiple Threads, EWS and WebDAV usage.

This tutorial is for C# .NET framework application. If you want to send email in Windows Store Apps (Window RT/Metro Style App), please go to Send Email in C# from Windows Store Apps - XAML - Tutorial

Tutorial Index

Send Email in A Simple C# Project using SMTP protocol

Installation

EASendMail is a SMTP component which supports all operations of SMTP/ESMTP protocols (RFC 821, RFC 822, RFC 2554). It also supports Exchange Web Service (EWS) and WebDAV protocols. Before you can use the following example codes, you should download the EASendMail Installer and install it on your machine at first.

Send email in a simple C# project

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.

send email in c# console project

Add Reference of EASendMail to Visual Stuido C#.NET Project

To use EASendMail SMTP Component in your project, the first step is "Add reference of EASendMail to your project". Please create/open your project with Visual Studio.NET, then choose menu->"Project"->"Add Reference"->".NET"->"Browse...", and choose the EASendMail{version}.dll from your disk, click "Open"->"OK", the reference of EASendMail will be added to your project, and you can start to use EASendMail to send email in your project.

add reference in c#

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 1.1, 2.0, 3.5, 4.0, 4.5 and .Net Compact Framework 2.0, 3.5.

File .NET Framework Version
EASendMail.dll Built with .NET Framework 1.1
It requires .NET Framework 1.1, 2.0, 3.5 or later version.
EASendMail20.dll Built with .NET Framework 2.0
It requires .NET Framework 2.0, 3.5 or later version.
EASendMail35.dll Built with .NET Framework 3.5
It requires .NET Framework 3.5 or later version.
EASendMaill40.dll Built with .NET Framework 4.0
It requires .NET Framework 4.0 or later version.
EASendMaill45.dll Built with .NET Framework 4.5
It requires .NET Framework 4.5 or later version.
EASendMailCF20.dll Built with .NET Compact Framework 2.0
It requires .NET Compact Framework 2.0, 3.5 or later version.
EASendMailCF35.dll Built with .NET Compact Framework 3.5
It requires .NET Compact Framework 3.5 or later version.

[C# - Send Email using SMTP - Example]

Now add the following codes to the project and change From, To, Server, User and Password to corresponding value. The following example codes demonstrate how to send email using SMTP protocol in C# project.

using System;
using System.Collections.Generic;
using System.Text;
using EASendMail; //add EASendMail namespace
 
namespace mysendemail
{
    class Program
    {
        static void Main(string[] args)
        {
            SmtpMail oMail = new SmtpMail("TryIt");
            SmtpClient oSmtp = new SmtpClient();
        
            // 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";
 
            // 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";
 
            // If your smtp server requires TLS connection, please add this line
            // oServer.ConnectType = SmtpConnectType.ConnectSSLAuto;

            // If your smtp server requires implicit SSL connection on 465 port, please add this line
            // oServer.Port = 465;
            // oServer.ConnectType = SmtpConnectType.ConnectSSLAuto;
 
            try
            {
                Console.WriteLine("start to send email ...");
                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);
            }
        }
    }
}

If you set everything right, you can get "email was sent successfully". If you get "failed to send email with the following error:", then please have a look at the following section.

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.

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.

c# console email sample

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:

Header Property
From SmtpMail.From
Reply-To SmtpMail.ReplyTo
Sender SmtpMail.Sender
Return-Path SmtpMail.ReturnPath
  • 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:

"No Such Host" exception

This error means DNS server cannot resolve SMTP server, you should check if you input correct server address. If your server address is correct, you should check if your DNS server setting is correct.

Common "Networking Connection" Exception

This error means there is a problem with networking connection to SMTP server. You can use Windows built-in Telnet command to detect the networking connection.

Using Telnet to detect networking connection to SMTP server

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:

detect SMTP connection using telnet

SMTP 25, 587, 465 port

25 port is the default SMTP server port to receive email. However, some ISP block outbound 25 port to prevent user to send email directly to other SMTP server. Therefore, many email providers also provide an alternative port 587 to receive email from such users. 465 port is the common port used to receive email over implicit SSL connection. If you use telnet to test 465 port, it doesn't return the "220...", because it requires SSL hand shake. But if the connection is ok, telnet returns a flash cursor.

"5xx ... IP address block or on black list or bad reputation" Exception

This error means SMTP server blocks your IP address or email content. You can try to set user/password in your codes to do user authentication and try it again. If email client set user authentication, most SMTP servers do not check client source IP address in black list.

"5xx user authenticaton" Exception

TThis error means user authentication is failed, you should check whether you input correct user/password. Password is always case-sensitive.

"5xx relay denied" Exception

For anti-spam policy, most SMTP servers do not accept the email to outbound domain without user authentication. You should set user/password in the codes and try it again.

"5xx Must issue a STARTTLS command first"

This error means SMTP server requires SSL/TLS connection. You should enable SSL/TLS connection like this:

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

"No supported authentication marshal found!"

This error means SMTP server doesn't support user authentication or it requires user authentication over SSL/TLS connection. You can try to remove user/password in your codes and try it again.

Other error returned by SMTP server

If SMTP server returns an error, it usually returns description about this error. Some descriptions also include a HTTP link, you can go to this linked web page to learn more detail. You can also use the following codes to generate a log file to learn all SMTP session between client and server.

[C# - Using log file to detect SMTP server response - Example]

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.

Next: Send email over SSL/TLS in C# >

Expand All Sections >> 1  2  3  4  5  6  7  8  9  10  11  12  13  14  15  16  17  18  19  

Appendix

Process Bounced Email (Non-Delivery Report) and Email Tracking
Bulk Email Sender Guidelines

Comments

If you have any comments or questions about above example codes, please click here to add your comments.

Send Email - C# - VB6 - Visual Basic - VC++ - C++/CLI - Delphi

Retrieve Email and Parse Email - C# - VB6 - Visual Basic - VC++ - C++/CLI - Delphi

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