procedure TForm1.Button1Click(Sender: TObject);
var
  ms: TMemoryStream;
begin
  IdPOP31.Host := 'neillans.co.uk';
  IdPOP31.Username := 'test@neillans.co.uk';
  IdPOP31.Password := '**GG$(';
  IdPOP31.Connect;
  If IdPOP31.CheckMessages > 0 Then
  Begin
    ms := TMemoryStream.Create;
    try
      IdPOP31.Retrieve(1, IdMessage1); 
      IdMessage1.SaveToStream(ms);
      Memo1.Lines.Add('Size: '   ms.Size);
    finally
      ms.Free;
    end;
  End;
  IdPOP31.Disconnect;
end;    

procedure TForm1.Button1Click(Sender: TObject);
var
  ms: TMemoryStream;
  i: integer;
begin
  IdPOP31.Host := 'neillans.co.uk';
  IdPOP31.Username := 'test@neillans.co.uk';
  IdPOP31.Password := '**GG$(';
  IdPOP31.Connect;
  for i := 1 to IdPOP31.CheckMessages do
  Begin
    ms := TMemoryStream.Create;
    try
      IdPOP31.Retrieve(i, IdMessage1); 
      IdMessage1.SaveToStream(ms);
      Memo1.Lines.Add('第 '   IntToStr(i)   ' 個附檔 Size: '   ms.Size);
    finally
      ms.Free;
    end;
  End;
  IdPOP31.Disconnect;
end;

     IdMessage1.MessageParts.CountParts;  // update AttachmentCount
      AttachmentCountEdit.Text :=
IntToStr(IdMessage1.MessageParts.AttachmentCount);
      AttachmentFileNamesEdit.Text := '';
      AttachmentFileSize := 0;
      for i := 0 to IdMessage1.MessageParts.Count - 1 do
        if IdMessage1.MessageParts.Items[i] is TIdAttachment then
          begin
            FileName := IdMessage1.MessageParts.Items[i].StoredPathName;
            try
              fs := TFileStream.Create(FileName, fmOpenRead or
fmShareDenyNone);
              try
                AttachmentFileSize := AttachmentFileSize   fs.Size;
              finally
                fs.Free;
              end;
            except
            end;
            FileName :=
TIdAttachment(IdMessage1.MessageParts.Items[i]).FileName;
            if AttachmentFileNamesEdit.Text <> '' then
              AttachmentFileNamesEdit.Text := AttachmentFileNamesEdit.Text  
' , ';
            AttachmentFileNamesEdit.Text := AttachmentFileNamesEdit.Text  
FileName;
            AttachmentFileSizeLabel.Caption := 'Attachment File Size: '  
IntToStr(AttachmentFileSize);
          end;