[Descendents]

ok el problema es outlook express.

Prueba esto

procedure TForm1.Button1Click(Sender: TObject);
const
  olMailItem = 0;
var
  Outlook, MailItem: OLEVariant;
begin
  try
    Outlook := GetActiveOleObject('Outlook.Application');
  except
    Outlook := CreateOleObject('Outlook.Application');
  end;

  MailItem := Outlook.CreateItem(olMailItem);
  MailItem.Recipients.Add('delphi at elists.org');
  MailItem.Subject := 'your subject';
  MailItem.Body := 'Visit: http://www.elists.org/mailman/listinfo/delphi';
  MailItem.Attachments.Add('C:\autoexec.bat');
  MailItem.Send;

  Outlook := Unassigned;
end;

Uses
Comobj


Suerte, a vder si sirve de algo.
Saludos