A slightly elegant stop-gap solution, using Apache rewrites:
RewriteEngine On
RewriteBase /
RewriteRule ^(.*)$ http://newdomain.com/$1 [L,R=302]
Stick that into an .htaccess
file in the web root of the site in question. This will take all requests to your server and rewrite them to http://newdomain.com/{whatever page was specified}
.
But if you want a permanent solution to ensure that your old domain points to your new server, you will have to gain access to the DNS because by redirecting your visitors, they are leaving your old domain name (which is probably something you don't want in the long term).