All domains need standard mailboxes (see RFC-2142) to receive e-mail for administrative and technical purposes. If your domain doesn't have them set up it can cost you a lot, especially since new domain registration rules by ICANN can cost you your domain if you can't receive notices at those addresses. Here's a list of the addresses you need to have set up and what they're generally used for:
- postmaster - e-mail and related matters, domain administration.
- hostmaster - DNS, issues with specific systems, domain administration.
- webmaster - web sites and HTTP servers.
- abuse - inappropriate or illegal behavior by users on machines in your domain.
- noc - network operations and infrastructure issues regarding your domain.
- security - security bulletins, reports and inquiries, overlaps with abuse.
- admin, administrator - Not part of RFC-2142, but recent ICANN domain registration rules changes have added these addresses as standard contact points for registration verification. They're more from the Windows world, but since having mail to them bounce can cause your registrar to suspend your domain it's best to have them working.
There are other mailboxes defined in RFC-2142, but they aren't mandatory and you probably won't be running services they'd be used for. One easy way of handling these is to forward all of them, along with root, to your own mailbox. That way all the critical e-mail ends up on one place and you're checking it regularly anyway. If you've got a larger shop with several people managing your network and systems, you'll want to forward those addresses to the person/people responsible for that area of operations.