(Delphi DLL) How to Download Messages in MessageSet One at a Time

If a message set contains a huge number of emails, it's NOT a good idea to try to download all at once into an email bundle using a method such as FetchBundle. It's better to iterate over the messages in the set to download one by one.

Chilkat for Delphi Downloads Chilkat non-ActiveX DLL for Delphi Chilkat ActiveX DLL for Delphi * The examples here use the non-ActiveX DLL.

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Imap, Email, MessageSet;

...

procedure TForm1.Button1Click(Sender: TObject);
var
imap: HCkImap;
success: Boolean;
fetchUids: Boolean;
messageSet: HCkMessageSet;
i: Integer;
email: HCkEmail;

begin
// This example requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

imap := CkImap_Create();

// Connect using TLS.
CkImap_putSsl(imap,True);
CkImap_putPort(imap,993);
success := CkImap_Connect(imap,'imap.example.com');
if (success <> True) then
  begin
    Memo1.Lines.Add(CkImap__lastErrorText(imap));
    Exit;
  end;

// Authenticate
success := CkImap_Login(imap,'email_account_login','email_account_password');
if (success <> True) then
  begin
    Memo1.Lines.Add(CkImap__lastErrorText(imap));
    Exit;
  end;

// Select an IMAP mailbox
success := CkImap_SelectMailbox(imap,'Inbox');
if (success <> True) then
  begin
    Memo1.Lines.Add(CkImap__lastErrorText(imap));
    Exit;
  end;

// Search for messages and return a set of matching messages.
// (This example will simply search for ALL messages.)
fetchUids := True;
messageSet := CkImap_Search(imap,'ALL',fetchUids);
if (CkImap_getLastMethodSuccess(imap) <> True) then
  begin
    Memo1.Lines.Add(CkImap__lastErrorText(imap));
    Exit;
  end;

Memo1.Lines.Add('Number of messages = ' + IntToStr(CkMessageSet_getCount(messageSet)));

i := 0;
while i < CkMessageSet_getCount(messageSet) do
  begin
    email := CkImap_FetchSingle(imap,CkMessageSet_GetId(messageSet,i),fetchUids);
    if (CkImap_getLastMethodSuccess(imap) <> True) then
      begin
        Memo1.Lines.Add(CkImap__lastErrorText(imap));
        CkMessageSet_Dispose(messageSet);
        Exit;
      end;
    Memo1.Lines.Add(CkEmail__from(email) + '; ' + CkEmail__subject(email));
    CkEmail_Dispose(email);

    i := i + 1;
  end;

CkMessageSet_Dispose(messageSet);

Memo1.Lines.Add('OK');

CkImap_Dispose(imap);

end;