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Retrieve Mail From a POP3 Server Using C#

, 19 Jan 2002
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A simple program for retrieving mails from a POP3 server, based on RFC 1725.

Sample Image - GUI.gif

Introduction

In this article, I'll show you how to retrieve mail from POP server based on RFC 1725.

Algorithm for Retrieving Mail

To retrieve mail from POP server, I just follow rule of RFC 1725. You also can download that paper (RFC 1725). 

Here's the algorithm:   

 Client   : +OK Server POP  Ready!!
 Client   : USER xxx
 Server   : +OK
 Client   : PASS yyy
 Server   : +OK user successfully logged on
 Client   : STAT
 Server   : +OK n m
 Client   : RETR 1
 Server   : +OK
               ---{ data }-----
 Client   : QUIT
 Server   : +OK Server POP signing off

Implementation

It's easy to implement an application if we know the algorithm to retrieve mail from a POP server. In this article, I use the TcpClient and NetworkStream classes. Firstly, declare public variables:

 public TcpClient Server;
 public NetworkStream NetStrm;
 public StreamReader  RdStrm;
 public string Data;
 public byte[] szData;
 public string CRLF = "\r\n";

Here's the code for when the Connect Button is clicked:

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

    // create server POP3 with port 110
    Server = new TcpClient(POPServ.Text,110);
    Status.Items.Clear();

    try
    {
        // initialization
        NetStrm = Server.GetStream();
        RdStrm= new StreamReader(Server.GetStream());
        Status.Items.Add(RdStrm.ReadLine());

        // Login Process
        Data = "USER "+ User.Text+CRLF;
        szData = System.Text.Encoding.ASCII.GetBytes(Data.ToCharArray());
        NetStrm.Write(szData,0,szData.Length);
        Status.Items.Add(RdStrm.ReadLine());

        Data = "PASS "+ Passw.Text+CRLF;
        szData = System.Text.Encoding.ASCII.GetBytes(Data.ToCharArray());
        NetStrm.Write(szData,0,szData.Length);
        Status.Items.Add(RdStrm.ReadLine());

        // Send STAT command to get information ie: number of mail and size
        Data = "STAT"+CRLF;
        szData = System.Text.Encoding.ASCII.GetBytes(Data.ToCharArray());
        NetStrm.Write(szData,0,szData.Length);
        Status.Items.Add(RdStrm.ReadLine());

        // change enabled - disabled button
        ConnectBtn.Enabled = false;
        DisconnectBtn.Enabled = true;
        RetrieveBtn.Enabled = true;

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

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

Here's the code for when the Disconnect Button is clicked:

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

    // Send QUIT command to close session from POP server
    Data = "QUIT"+CRLF;
    szData = System.Text.Encoding.ASCII.GetBytes(Data.ToCharArray());
    NetStrm.Write(szData,0,szData.Length);
    Status.Items.Add(RdStrm.ReadLine());

    //close connection
    NetStrm.Close();
    RdStrm.Close();

    // change enabled - disabled button
    ConnectBtn.Enabled = true;
    DisconnectBtn.Enabled = false;
    RetrieveBtn.Enabled = false;

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

Here's code when Retrieve Button clicked:

private void RetrieveBtn_Click(object sender, System.EventArgs e)
{
    // change cursor into wait cursor
    Cursor cr = Cursor.Current;
    Cursor.Current = Cursors.WaitCursor;
    string szTemp;
    Message.Clear();
    try
    {
        // retrieve mail with number mail parameter
        Data = "RETR "+ Number.Text+CRLF;
        szData = System.Text.Encoding.ASCII.GetBytes(Data.ToCharArray());
        NetStrm.Write(szData,0,szData.Length);

        szTemp = RdStrm.ReadLine();
        if(szTemp[0]!='-') 
        {
        
            while(szTemp!=".")
            {
                Message.Text += szTemp;
                szTemp = RdStrm.ReadLine();
            }
        }
        else
        {
            Status.Items.Add(szTemp);
        }
        
        // back to normal cursor
        Cursor.Current = cr;

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

}

Testing

Build and run this project. Set the POP server, user and password. After that you'll get a response message from the POP server (you can see on status box) ie: +OK 2 624 if success or -ERR if fail. The words "+OK 2 624" mean you have two emails and total size 624.

Now, you can set the mail message number and then click Retrieve button. Then you'll get the mail according to the mail number that you wrote on Mail Number Box.

Reference

  • MSDN for .NET framework
  • RFC 1725

History

20 Jan 2002 - fixed non-critical GUI problem

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

 
GeneralRe: don't work with pop.gmail.com PinmemberDanie de Kock7-Jun-10 8:53 
GeneralRe: don't work with pop.gmail.com PinmemberT. Abdul Rahman9-Dec-11 20:01 
Generalreceive mail from hotmail Pinmemberfatz1213-Apr-09 12:27 
GeneralRe: receive mail from hotmail PinmemberMember 890050230-Apr-12 7:11 
Generalfrom hotmail Pinmemberfatz1213-Apr-09 12:07 
QuestionPOP3 PinmemberShu-Wen8-Mar-09 21:17 
QuestionWhat is the "Mail Number"? PinmemberONeil Tomlinson17-Dec-08 0:51 
AnswerRe: What is the "Mail Number"? Pinmemberjuanocen8-Jan-09 1:39 
It is an ID number the server gives to each message. Begins in 1 and ends in message count.You must use this ID numbers to for example Retrieve the message (RET 3) means you are reading the third message... also for other things like Deleting messages from the server (DELE 2)--> Delete message with ID 2.
 
Each time you get fresh information from the server this IDs can change, they are only useful for the current session.
 
Good Luck.
Generalim using pop3mimeclient Pinmemberjayas22-Mar-08 2:31 
Questionhi Good pls help me Pinmemberyogarajan ganesan14-Mar-08 2:32 
GeneralError In This Code Pinmember~V~18-Feb-08 0:56 
GeneralRe: Error In This Code PinmemberYesugey3-Aug-09 4:28 
GeneralValue can not be null [modified] Pinmembernpipaliya29-Nov-07 18:57 
Generalconnection attempts failed Pinmemberjain_abhishek_siet12-Sep-07 22:15 
QuestionNeed the help Pinmemberminpeng200610-Sep-07 7:08 
Generalhelp me!!! Pinmembersaobangtn2231-Aug-07 17:01 
QuestionNeed help Pinmemberkanzz7-Aug-07 22:03 
Generalproblem with retreiving mail PinmemberMostafa_Ismail22-Jul-07 2:41 
QuestionHow To read Attached doc file from pop3 [modified] Pinmemberu3033827-Apr-07 21:31 
QuestionCan it be stored in outlook? Pinmemberzjkida25-May-06 8:19 
GeneralProblem in POP3 Server PinmemberSR Ranjini19-Apr-06 19:24 
GeneralRe: Problem in POP3 Server Pinmembergohil7715-Jun-06 23:09 
GeneralQuestion Pinmemberkraster19-Apr-06 1:41 
GeneralThanks for the code PinsussLalitha V19-Oct-05 5:17 
GeneralConnect to SSL POP3 PinsussAnonymous23-Aug-05 7:08 

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