Since Synonoly released version 6 of Disk Station Manager (DSM), things in the Apache configuration where changed. I used to have a reverse proxy using Apache mod_proxy. The old configuration was stored in /etc/httpd/sites-enabled-user/httpd-vhost.conf (or httpd-ssl-vhost.conf in my case since I use SSL). The new configuration to put your reverse proxy configuration can be found in: /usr/local/etc/httpd/sites-enabled/httpd-vhost.conf-user.

To set-up a reverse proxy to services listening on strange ports, like SabNZBd, SickRage / SickBeard, CouchPotato or Transmission use these lines as an example and edit them to your needs. With this configuration you should be able to download your CentOS images from usenet without getting blocked by the company firewall…

<Location /sb>
  ProxyPass http://127.0.0.1:8083/sb
  ProxyPassReverse http://127.0.0.1:8083/sb
</Location>

<Location /sabnzbd>
  ProxyPass http://127.0.0.1:8080
  ProxyPassReverse http://127.0.0.1:8080
</Location>

<Location /couchpotato>
  ProxyPass http://127.0.0.1:5053/couchpotato
  ProxyPassReverse http://127.0.0.1:5053/couchpotato
</Location>

<Location /transmission>
  ProxyPass http://127.0.0.1:9091/transmission
  ProxyPassReverse http://127.0.0.1:9091/transmission
</Location>