Set up mail-receiver, but now site won't send any emails?

[Jagster (Jakke Flemming)]

I was thinking this topic, where you were participating too:

Will UFW limit Discourse too?

How can Discourse bypass UFW? I had enabled only port 22 so all other ports should be closed then. But a forum worked anyway. How’s that possible? DigitalOcean droplet, but that should not mean anything. And no one-click install, but official way. This is not a pure support question, but we don’t have here a catogory named Stupid basic questions by beginners