Delphi - Mark Email as Read in POP3

If you want to leave a copy of email on the server, you should not call Delete method. However, there is a problem, how can you know if the email has already been downloaded (read)? If there is a way to identify the downloaded email, you can avoid downloading the duplicated email from your POP3/IMAP4 server.

Every email has a unique identifier (UIDL) on POP3 server. POP3 UIDL is only unique in the email life time. That means if the email was deleted from the server, other email can use the old unique identifier. Another problem is: UIDL in POP3 server can be any number or characters, so we cannot use UIDL as the file name, because UIDL may contain invalid characters for file name.

To solve this problem, we have to store the UIDL to a txt file and synchronize it with server every time.

The following delphi example codes demonstrate how to mark the email as downloaded/read on POP3 server.

Installation

Before you can use the following sample codes, you should download the EAGetMail Installer and install it on your machine at first. Full sample projects are included in this installer.

Add Reference

To use EAGetMail ActiveX Object in your Delphi project, the first step is “Add Unit file of EAGetMail to your project”. Please go to C:\Program Files\EAGetMail\Samples_Delphi\pop3_imap4_simple.delphi or C:\Program Files (x86)\EAGetMail\Samples_Delphi\pop3_imap4_simple.delphi folder, find EAGetMailObjLib_TLB.pas, and then copy this file to your project folder.

// include EAGetMailObjLib_TLB unit to your Delphi Project
unit Unit1;

interface

uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, EAGetMailObjLib_TLB, StdCtrls;

Then you can start to use it in your Delphi Project.

You can also create EAGetMailObjLib_TLB.pas manually by Delphi like this:

  • Delphi 7 or eariler version

    First of all, create a standard delphi project: select menu Project -> Import Type Library, checked EAGetMail ActiveX Object and click Create Unit. Then include EAGetMailObjLib_TLB in your project.

    add reference in Delphi
  • Delphi XE or later version

    First of all, create a standard delphi project: select menu Component -> Import component... -> Import a type library -> checked EAGetMail ActiveX Object, have Generate Component Wrapper checked and click “Create Unit”. Then include EAGetMailObjLib_TLB in your project.

Delphi - Mark Email as Read in POP3 - Example

The following example codes demonstrate marking email as read/downloaded on POP3 server. In order to run it correctly, please change email server, user, password, folder, file name value to yours.

Note

To get full sample projects, please download and install EAGetMail on your machine.

Unit Unit1;

Interface

Uses
    Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
    Dialogs, StdCtrls, StrUtils, EAGetMailObjLib_TLB;

Type
    TForm1 = Class(TForm)
    Button1: TButton;
    Procedure Button1Click(Sender: TObject);

    // UIDL functions
    Procedure LoadUIDL();
    Procedure UpdateUIDL();
    Procedure SyncUIDL(oServer: TMailServer; infos: OleVariant);
    Function FindExistedUIDL(oServer: TMailServer; UIDL: WideString): Boolean;
    Procedure AddUIDL(oServer: TMailServer; UIDL: WideString);

    private
        { Private declarations }
    public
        { Public declarations }
    End;

Const
    MailServerPop3 = 0;
    MailServerImap4 = 1;

Var
    Form1: TForm1;
    m_curpath: WideString;
    m_uidlfile: WideString;
    m_uidls: WideString;

Implementation

{$R *.dfm}

Procedure TForm1.LoadUIDL();
Var
    oTools: TTools;
Begin
    oTools := TTools.Create(Application);
    m_uidls := '';
    m_uidls := oTools.ReadTextFile(m_uidlfile, 0);
End;

Procedure TForm1.UpdateUIDL();
Var
    oTools: TTools;
Begin
    Try
        oTools := TTools.Create(Application);
        oTools.WriteTextFile(m_uidlfile, m_uidls, 0);
    Except
        On ep:Exception Do
        ShowMessage('Update UIDL Error: ' + ep.Message);
    End;
End;

Procedure TForm1.SyncUIDL(oServer: TMailServer; infos: OleVariant);
Var
    index, i, UBound: Integer;
    curpref, uidlpref, t, localuidl: WideString;
    uidls, newuidls: WideString;
    bRemove, bExistOnServer: boolean;
    oInfo: IMailInfo;
Begin
    uidlpref := LowerCase(oServer.Server) + '#' +
        LowerCase(oServer.User) + ' ';

    uidls := m_uidls;
    UBound := VarArrayHighBound(infos, 1);

    While true Do
    Begin
        index := Pos(#13#10, uidls);
        If(index <= 0) Then
        break;

        t := LeftStr(uidls, index-1);
        uidls := MidStr(uidls, index + 2, Length(uidls)-index-2);
        bRemove := false;
        If Length(t) > Length(uidlpref) Then
        Begin
            curpref := LeftStr(t, Length(uidlpref));
            // this UIDL belongs to current server/user
            If CompareStr(curpref, uidlpref) = 0 Then
            Begin
                localuidl := MidStr(t, Length(curpref)+1, Length(t)-Length(curpref));
                bExistOnServer := false;
                For i := 0 To UBound Do
                Begin
                oInfo := IDispatch(VarArrayGet(infos, i)) As IMailInfo;
                If CompareStr(oInfo.UIDL, localuidl) = 0 Then
                    Begin
                    bExistOnServer := true;
                    break;
                    End;
                End;

                If Not bExistOnServer Then
                bRemove := true;

                If trim(t) = '' Then
                bRemove := true;
            End;
        End;

        If Not bRemove Then
        newuidls := newuidls + t + #13#10;
    End;

    m_uidls := newuidls;
End;

Function TForm1.FindExistedUIDL(oServer: TMailServer; UIDL: WideString): Boolean;
Var
    s: WideString;
    index: Integer;
Begin
    s := LowerCase(oServer.Server) + '#' +
            LowerCase(oServer.User) + ' ' + UIDL + #13#10;

    index := Pos(s, m_uidls);
    If index > 0 Then
        FindExistedUIDL := true
    Else
        FindExistedUIDL := false;
End;

Procedure TForm1.AddUIDL(oServer: TMailServer; UIDL: WideString);
Begin
    m_uidls := m_uidls + LowerCase(oServer.Server) + '#' +
        LowerCase(oServer.User) + ' ' + UIDL + #13#10;
End;

Function TForm1.SearchFolder(folders: OleVariant; name: WideString)
:IImap4Folder;
Var
    i, UBound: Integer;
    folder: IImap4Folder;
Begin
    UBound := VarArrayHighBound(folders, 1);
    For i:= 0 To UBound Do
    Begin
        folder := IDispatch(VarArrayGet(folders,i)) As IImap4Folder;
        If CompareText(folder.Name, name) = 0 Then
        Begin
        Result := folder;
        exit;
        End;

        // Search folder in sub-folders
        folder := SearchFolder(folder.SubFolders, name);
        If Not (folder = nil) Then
        Begin
            Result := folder;
            exit;
        End;
    End;
    // No folder found
    Result := nil;
End;

Procedure TForm1.Button1Click(Sender: TObject);
Var
    oMail: IMail;
    oClient: TMailClient;
    oServer: TMailServer;
    oTools: TTools;
    infos: OleVariant;
    i, UBound, Count: Integer;
    oInfo: IMailInfo;
    mailFolder: WideString;
    fileName: WideString;
    leaveCopy: Boolean;
Begin
    Try
        oTools := TTools.Create(Application);

        // Create a folder named "inbox" under
        // current directory to store the email files
        mailFolder := GetCurrentDir() + '\inbox';
        m_curpath := GetCurrentDir();
        m_uidlfile := m_curpath + '\uidl.txt';
        oTools.CreateFolder(mailFolder);

        oServer := TMailServer.Create(Application);
        oServer.Server := 'pop3.emailarchitect.net';
        oServer.User := 'test@emailarchitect.net';
        oServer.Password := 'testpassword';
        oServer.Protocol := MailServerPop3;

        // If your server requires SSL connection
        // Please add the following codes
        // oServer.SSLConnection := true;
        // oServer.Port := 995;

        // leave a copy of message on server
        leaveCopy := true;
        oClient := TMailClient.Create(Application);
        oClient.LicenseCode := 'TryIt';

        oClient.Connect1(oServer.DefaultInterface);
        ShowMessage('Connected!');

        // UIDL is the identifier of every email on POP3/IMAP4 server, to avoid retrieve
        // the same email from server more than once, we record the email uidl retrieved every time
        // if you delete the email from server every time and not to leave a copy of email on
        // the server, then please remove all the function about uidl.
        LoadUIDL();

        infos := oClient.GetMailInfos();
        UBound := VarArrayHighBound(infos, 1);
        Count := UBound+1;

        SyncUIDL(oServer, infos);

        ShowMessage(Format('Total %d email(s)', [Count]));

        For i := 0 To UBound Do
        Begin
        oInfo := IDispatch(VarArrayGet(infos, i)) As IMailInfo ;
        ShowMessage(Format('Index: %d; Size: %d; UIDL: ' + oInfo.UIDL,
        [oInfo.Index, oInfo.Size]));

        If FindExistedUIDL(oServer, oInfo.UIDL) Then
            continue; // this email has been downloaded, Do Not receive it again

        // Generate a random file name by current local datetime,
        // You can use your method to generate the filename if you do not like it
        fileName := mailFolder + '\' + oTools.GenFileName(i) + '.eml';

        // Receive email from POP3 server
        oMail := oClient.GetMail(oInfo);

        ShowMessage('From: ' + oMail.From.Address + #13#10 +
            'Subject: ' + oMail.Subject);

        // Save email to local disk
        oMail.SaveAs(fileName, true);

        If leaveCopy Then
        Begin
            //add the email uidl to uidl file to avoid we retrieve it next time.
            AddUIDL(oServer, oInfo.UIDL);
        End
        Else
        Begin
            // Mark email as deleted from IMAP4 server
            oClient.Delete(oInfo);
        End;
        End;

        // Quit and purge emails marked as deleted from POP3 server
        oClient.Quit;

    Except
        On ep:Exception Do
        ShowMessage('Error: ' + ep.Message);
    End;

    UpdateUIDL();

End;

End.

UIDL Manager

UIDLManager provides an easier way to maintain UIDL between your server and your local client. It stores UIDL collection to a local disk file and you can use this object to add, remove and search UIDL with this local file.

Work with UIDL Manager

32bit/x64 ActiveX DLL

Seperate builds of run-time dll for 32 and x64 platform

File Platform
Installation Path\EAGetMailObj.dll 32 bit
Installation Path\x64\EAGetMailObj.dll 64 bit

Distribution

  • Standard EXE

    For VB6, C++, Delphi or other standard exe application, you can distribute EAGetMailObj.dll with your application to target machine without COM-registration and installer. To learn more detail, please have a look at Registration-free COM with Manifest File.

  • Script

    For ASP, VBScript, VBA, MS SQL Stored Procedure, you need to install EAGetMail on target machine by EAGetMail installer, both 32bit/x64 DLL are installed and registered.

Appendix

Comments

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