@Angle Basically, yes. Look up "MX records". It's how email servers find each other.

DNS is sort of between centralized and decentralized; anyone can run their own DNS server but they need to talk to a registrar to get it connected to the rest of the DNS hierarchy. Most registrars are run as more-or-less-virtuous nonprofits and people get *pissed* when they aren't, so this has mostly worked okay so far.