procedure TForm1.Button1Click(Sender: TObject);
begin
  with NMSMTP1 do
  begin
    Host := 'smtp.mailserver.com';
    UserID := '___Nikolay';
    Connect;

    PostMessage.FromAddress := 'DelphiWorld@mail.ru';
    PostMessage.ToAddress.Text := 'bestprogramming@mail.ru';
    PostMessage.Body.Text := 'Текст письма';
    PostMessage.Subject := 'Тема письма';
    SendMail;
  end;
end;