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Sending Mail Using C# via SMTP

, 19 Dec 2001
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A simple application for sending mail via SMTP server using C#

Introduction

This project shows how to send mail via an SMTP server using C#.

How to Send Mail via SMTP

Based on RFC 821 about Simple Mail Transfer Protocol, it's very easy to send mail via SMTP. Here's the handshaking for sending mail:

 Receiver: 220 server.com Simple Mail Transfer Service Ready
 Sender  : HELO server.com
 Receiver: 250 server.com
 Sender  : MAIL FROM: <agusk@host.com>
 Receiver: 250 OK
 Sender  : RCPT TO: <myhoney@host.com>
 Receiver: 250 OK
 Sender  : DATA
 Receiver: 354 Start mail input: end with <CRLF>.<CRLF>
 Sender  : all data like From, To, Subject, Body etc. 
           ended with <CRLF>.<CRLF>
 Receiver: 250 OK
 Sender  : QUIT
 Receiver: 250 server.com closing transmission channel

Building the Application Using C#

Here's a model of the GUI:

add these code lines for when the use clicks the Send button:

 private void SendBtn_Click(object sender, System.EventArgs e)
{
    // change cursor into wait cursor
    Cursor cr = Cursor.Current;
    Cursor.Current = Cursors.WaitCursor;

    // create server SMTP with port 25
    TcpClient SmtpServ = new TcpClient(ServSMTP.Text,25);
    string Data;
    byte[] szData;
    string CRLF = "\r\n";
    LogList.Items.Clear();            

    try
    {
        // initialization
        NetworkStream NetStrm = SmtpServ.GetStream();
        StreamReader  RdStrm= new StreamReader(SmtpServ.GetStream());
        LogList.Items.Add(RdStrm.ReadLine());
            
        // say hello to server and send response into log report
        Data = "HELLO server " + CRLF;                
        szData = System.Text.Encoding.ASCII.GetBytes(Data.ToCharArray());
        NetStrm.Write(szData,0,szData.Length);
        LogList.Items.Add(RdStrm.ReadLine());
        // send sender data
        Data = "MAIL FROM: " + "<" + sFrom.Text + ">" + CRLF;
        szData = System.Text.Encoding.ASCII.GetBytes(Data.ToCharArray());
        NetStrm.Write(szData,0,szData.Length);
        LogList.Items.Add(RdStrm.ReadLine());

        // send receiver data
        Data = "RCPT TO: " + "<" + sTo.Text + ">" + CRLF;
        szData = System.Text.Encoding.ASCII.GetBytes(Data.ToCharArray());
        NetStrm.Write(szData,0,szData.Length);
        LogList.Items.Add(RdStrm.ReadLine());

        // send DATA
        Data = "DATA " + CRLF;
        szData = System.Text.Encoding.ASCII.GetBytes(Data.ToCharArray());
        NetStrm.Write(szData,0,szData.Length);
        LogList.Items.Add(RdStrm.ReadLine());                

        // send content data
        Data = "SUBJECT: " + sSubject.Text + CRLF +
           sMessage.Text + CRLF + "." + CRLF;
        szData = System.Text.Encoding.ASCII.GetBytes(Data.ToCharArray());
        NetStrm.Write(szData,0,szData.Length);
        LogList.Items.Add(RdStrm.ReadLine());                

        // quit from server SMTP
        Data = "QUIT " + CRLF;
        szData = System.Text.Encoding.ASCII.GetBytes(Data.ToCharArray());
        NetStrm.Write(szData,0,szData.Length);
        LogList.Items.Add(RdStrm.ReadLine());                

        // close connection
        NetStrm.Close();
        RdStrm.Close();
        LogList.Items.Add("Close connection");
        LogList.Items.Add("Send mail successly..");

        // back to normal cursor
        Cursor.Current = cr;

    }
    catch(InvalidOperationException err)
    {
        LogList.Items.Add("Error: "+ err.ToString());
    }
}

Reference

  • Document RFC 821 and MSDN for .NET Development

License

This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

A list of licenses authors might use can be found here

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About the Author

Agus Kurniawan
Founder PE College
Indonesia Indonesia
He gradueted from Sepuluh Nopember Institute of Technology (ITS) in Department of Electrical Engineering, Indonesia. His programming interest is VC++, C#, VB, VB.NET, .NET, VBScript, Delphi, C++ Builder, Assembly,and ASP/ASP.NET. He's founder for PE College(www.pecollege.net), free video tutorial about programming, infrastructure, and computer science. He's currently based in Depok, Indonesia. His blog is http://geeks.netindonesia.net/blogs/agus and http://blog.aguskurniawan.net

Comments and Discussions

 
GeneralMy vote of 1 Pinmemberdandy_andy19-Apr-14 9:49 
Questionpassword PinmemberAETCoder19-Jun-11 11:07 
GeneralMy vote of 3 Pinmemberudhaya2code31-Jul-10 1:28 
Generalmail in C++ Pinmembermisa_qn23-Sep-08 22:47 
GeneralRe: mail in C++ Pinmemberurapola10-Nov-08 18:12 
GeneralHelp , please Pinmemberprogramet_nje15-Apr-08 7:38 
GeneralHelp , please Pinmemberprogramet_nje15-Apr-08 7:37 
Questions this sending mail trhough SMTP dependent on any mail cilent?? Pinmembertika123-Apr-07 0:03 
Generalhaving problem Pinmembermohsen.karami5-Nov-06 18:48 
QuestionAuthentication problem PinmemberDannyAdler23-Mar-06 15:54 

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