@oplik0 the SMTP didn't work either. But thank you very much for pointing at the other services! I've just tried SendGrid and it worked perfectly from the 1st attempt.
Check out the event lot page in the ACP (under advanced). The user's deletion event should have been logged, and the IP address should have been saved.
... as long as your NodeBB is new enough, that is 🙂
You can manage the categories permissions throught Administration Control Panel in order to hide it from unregistered users. Maybe theres some more options there.