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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

 
Questiontrouble with checked as not read emails on server Pin
ice_ok at 3-Apr-14 5:56
memberice_ok3-Apr-14 5:56 
Generalexception Pin
hammadsalik at 8-Mar-14 22:41
memberhammadsalik8-Mar-14 22:41 
QuestionSocketException Pin
Antz411 at 28-Feb-14 0:17
memberAntz41128-Feb-14 0:17 
QuestionGet the total number of emails in Inbox Pin
viragdesai at 30-Apr-13 21:15
memberviragdesai30-Apr-13 21:15 
QuestionI connect but I see no emails Pin
muslera at 4-Nov-12 13:09
membermuslera4-Nov-12 13:09 
Questiononly get a part of mails Pin
sbmzhcn at 21-Sep-12 23:54
membersbmzhcn21-Sep-12 23:54 
QuestionConnection problems! Pin
Member 3768609 at 24-Jul-12 1:11
memberMember 376860924-Jul-12 1:11 
QuestionI am getting the error Pin
T. Abdul Rahman at 9-Dec-11 20:38
memberT. Abdul Rahman9-Dec-11 20:38 
Generalvalue cannot be null ;parameter name : item Pin
yoga arista at 9-Feb-11 0:24
memberyoga arista9-Feb-11 0:24 
Generalmail folders Pin
stijnn_17 at 13-Dec-10 9:57
memberstijnn_1713-Dec-10 9:57 
GeneralRe: mail folders Pin
kirnyk at 25-Apr-11 5:37
memberkirnyk25-Apr-11 5:37 
Generalvalue can not be null... Pin
lsb_safari at 16-Sep-10 9:53
memberlsb_safari16-Sep-10 9:53 
QuestionHow to Read folder lik "junk" or any customized folder on mailserver? Pin
jymitra at 19-Jul-10 22:46
memberjymitra19-Jul-10 22:46 
GeneralDecode uft-8, iso-8859-1, ... Pin
João Batista Carvalho at 23-Mar-10 9:30
memberJoão Batista Carvalho23-Mar-10 9:30 
Questiongetting _ERRbad login Pin
Meena.G at 17-Jul-09 20:42
memberMeena.G17-Jul-09 20:42 
AnswerRe: getting _ERRbad login Pin
Manesh.C.S at 24-Feb-11 5:39
memberManesh.C.S24-Feb-11 5:39 
Generaldon't work with pop.gmail.com Pin
kyo00710 at 23-May-09 22:17
memberkyo0071023-May-09 22:17 
GeneralRe: don't work with pop.gmail.com Pin
Meetu Choudhary at 19-Aug-09 3:08
memberMeetu Choudhary19-Aug-09 3:08 
GeneralRe: don't work with pop.gmail.com Pin
Ram Prasad at 29-Nov-09 23:27
memberRam Prasad29-Nov-09 23:27 
GeneralRe: don't work with pop.gmail.com [modified] Pin
kyo00710 at 1-Dec-09 4:14
memberkyo007101-Dec-09 4:14 
GeneralRe: don't work with pop.gmail.com Pin
pratapraju at 5-Aug-10 7:24
memberpratapraju5-Aug-10 7:24 
GeneralRe: don't work with pop.gmail.com Pin
muslera at 4-Nov-12 13:03
membermuslera4-Nov-12 13:03 
GeneralRe: don't work with pop.gmail.com Pin
tyni at 8-Apr-10 12:34
membertyni8-Apr-10 12:34 
GeneralRe: don't work with pop.gmail.com Pin
Danie de Kock at 7-Jun-10 9:53
memberDanie de Kock7-Jun-10 9:53 
GeneralRe: don't work with pop.gmail.com Pin
T. Abdul Rahman at 9-Dec-11 21:01
memberT. Abdul Rahman9-Dec-11 21:01 
Generalreceive mail from hotmail Pin
fatz12 at 13-Apr-09 13:27
memberfatz1213-Apr-09 13:27 
GeneralRe: receive mail from hotmail Pin
Member 8900502 at 30-Apr-12 8:11
memberMember 890050230-Apr-12 8:11 
Generalfrom hotmail Pin
fatz12 at 13-Apr-09 13:07
memberfatz1213-Apr-09 13:07 
QuestionPOP3 Pin
Shu-Wen at 8-Mar-09 22:17
memberShu-Wen8-Mar-09 22:17 
QuestionWhat is the "Mail Number"? Pin
ONeil Tomlinson at 17-Dec-08 1:51
memberONeil Tomlinson17-Dec-08 1:51 
AnswerRe: What is the "Mail Number"? Pin
juanocen at 8-Jan-09 2:39
memberjuanocen8-Jan-09 2:39 
QuestionHow do I save the message in the Inbox\new foder Pin
nirmalamari at 11-Aug-08 10:00
membernirmalamari11-Aug-08 10:00 
AnswerRe: How do I save the message in the Inbox\new foder Pin
ONeil Tomlinson at 17-Dec-08 1:49
memberONeil Tomlinson17-Dec-08 1:49 
Generalim using pop3mimeclient Pin
jayas at 22-Mar-08 3:31
memberjayas22-Mar-08 3:31 
Questionhi Good pls help me Pin
yogarajan ganesan at 14-Mar-08 3:32
memberyogarajan ganesan14-Mar-08 3:32 
GeneralError In This Code Pin
~V~ at 18-Feb-08 1:56
member~V~18-Feb-08 1:56 
GeneralRe: Error In This Code Pin
Yesugey at 3-Aug-09 5:28
memberYesugey3-Aug-09 5:28 
GeneralValue can not be null [modified] Pin
npipaliya at 29-Nov-07 19:57
membernpipaliya29-Nov-07 19:57 
Generalconnection attempts failed Pin
jain_abhishek_siet at 12-Sep-07 23:15
memberjain_abhishek_siet12-Sep-07 23:15 
QuestionNeed the help Pin
minpeng2006 at 10-Sep-07 8:08
memberminpeng200610-Sep-07 8:08 
Generalhelp me!!! Pin
saobangtn22 at 31-Aug-07 18:01
membersaobangtn2231-Aug-07 18:01 
QuestionNeed help Pin
kanzz at 7-Aug-07 23:03
memberkanzz7-Aug-07 23:03 
Generalproblem with retreiving mail Pin
Mostafa_Ismail at 22-Jul-07 3:41
memberMostafa_Ismail22-Jul-07 3:41 
QuestionHow To read Attached doc file from pop3 [modified] Pin
u30338 at 27-Apr-07 22:31
memberu3033827-Apr-07 22:31 
QuestionCan it be stored in outlook? Pin
zjkida at 25-May-06 9:19
memberzjkida25-May-06 9:19 
GeneralProblem in POP3 Server Pin
SR Ranjini at 19-Apr-06 20:24
memberSR Ranjini19-Apr-06 20:24 
GeneralRe: Problem in POP3 Server Pin
gohil77 at 16-Jun-06 0:09
membergohil7716-Jun-06 0:09 
GeneralQuestion Pin
kraster at 19-Apr-06 2:41
memberkraster19-Apr-06 2:41 
GeneralThanks for the code Pin
Lalitha V at 19-Oct-05 6:17
sussLalitha V19-Oct-05 6:17 
GeneralConnect to SSL POP3 Pin
Anonymous at 23-Aug-05 8:08
sussAnonymous23-Aug-05 8:08 

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