Can EP cache non-Plone sites using simple rewrite_mode?
See the documentation about Using Simple Rewrite_Mode to Proxy Non-Plone Sites . Assuming that 1) the server is able to serve relative URLs correct for the proxy AND 2)the server sets the cache headers appropriately, then Enfold Proxy will cache the content. To determine whether the cache headers are set appropriately, consult the cacheability engine.