window.open("/_ui/core/email/author/EmailAuthor?p3_lkid={!Case.Id}&retURL=%{!Case.Id}","_blank","toolbar=yes, location=yes, directories=no, status=no, menubar=yes, scrollbars=yes, resizable=no, width=800, height=650");

location.replace('/email/author/emailauthor.jsp?retURL=/{!Case.Id}&p3_lkid={!Case.Id}&rtype=003&p2_lkid={!Case.ContactId}&template_id=00XCXXXXXXXXXXX&p26=support@xxx.com');