User-agent: *
Host: NEWdomainname.com

switch ($_SERVER['HTTP_HOST']) {
case "OLDdomainname.com":
                            header("Location: http://NEWdomainname.com".$_SERVER['REQUEST_URI']);
                            exit;
                            break;
case "www.OLDdomainname.com":
                            header("Location: http://www.NEWdomainname.com".$_SERVER['REQUEST_URI']);
                            exit;
                            break;

default:
}

RewriteEngine on
RewriteCond %{HTTP_HOST} ^OldDomain.com$ [OR]
RewriteCond %{HTTP_HOST} ^www.OldDomain.com$
RewriteRule ^(.*)$ http://www.NewDomain.com/$1 [R=301,L]