I've gotten a little more paranoid in recent years and started blocking outgoing requests, just as a defense in depth. So I would prevent clients from connecting to anything but 22, 80 and 443 (to start; I added more for things like WebRTC and Amazon Streaming which uses AWS). I found a checkout that was connecting over some random port and wouldn't work until that was unblocked. Fucking annoying and I'm just left wondering how long until they have a security breach through their non-standard proprietary bullshit.