<p>Open / forward the following <code>TCP</code> ports to your proxyserver's ip-address:</p> <pre><code>TCP / 80 (HTTP - client to server) TCP / 443 (HTTPS - client to server)</code></pre> <!-- !!! EXPLAIN WHY (to be able to request Let's Encrypt certificates)? --> <!-- !!! EXPLAIN WHY (to enable https connections to the webmail)? --> <!-- REFERENCES -->