The http.proxyHost and http.proxyPort system properties described in Configuring+Web+Proxy+Support+for+Confluence are only needed when Confluence (if deployed in a data centre or DMZ) needs to communicate with remote servers. In short, it is useful for letting outbound request go through the web proxy. If Confluence is deployed behind a reverse proxy (that only allows incoming requests via specific ports), you will need to set the proxyHost and proxyPort in the server.xml file of the bundled Tomcat server as described in this CAC KB page.