var_property = 'toolbar=0,location=0,directories=0,status=0,menubar=0,scrollbars=0,resizable=0,width=630,height=600';

 new_mail_window = window.open('temp_act.php?b_type=mmail','mmail_window',var_property);

 sel_form.action = "temp_act.php?b_type=mmail";
 sel_form.target = "mmail_window";
 sel_form.submit();