This is needed by WebRTC, that choses random ports (in a big range of something like 10000-65535) when establishing the connection.
If this is not possible, a workaround is possible by allowing outgoing both TCP & UDP on port 443. This will force your devices to use our relay servers. This can add a little latency to the call and is not the ideal solution.
A really minimal configuration would allow 443 only on TCP or UDP, altough we discourage this.