XF 2.2 Optimizing for CDN caching


Currently my site is caching static files on CDN.
I would like to extend caching to all forum pages, for guest users. Since they do not participate in the forums, they do not require real-time updates in the forums.

The problem now is to find out how to let the CDN know that a page is safe for caching.
I notice XF will always send cache-control no-cache
Can the header be overridden?
For example, if user is guest, then send Cache-Control: max-age=600