I am trying to get the expires header to work on the cache module. I am limiting what content can be accessed and then would like to cache that content. It is working to only server the specified content but it is not serving the expires header. The backend server is not set to send and expires header and with the code below I get a an expiration not specified result. Here is that portion of the conf file -

location ~* (\.jpg|\.png|\.gif|\.css|ThumbNail\.ashx|heartbeat\.htm)$ {

valid_referers
none
blocked
mysite.com
www.mysite.com
1.mysite.com
2.mysite.com
3.mysite.com
4.mysite.com;

if ($invalid_referer) {
return 444;
}

proxy_pass http://mysite_com;
proxy_cache_valid 200 301 302 1480m;
expires 5d;
proxy_cache dci;
proxy_cache_use_stale error timeout invalid_header updating;

}