Below is the email Mark E Jeftovic of EasyDNS posted to NANOG:
As some of you may know, we recently took over ZoneEdit.com and it's customer base.
We've found a domain on the system: rbl.orbitrbl.com which is delegated to zoneedit nameservers, broken (it is not allowed to zone transfer from it's designated master), unresponsive (account owner is not answering email, has an address in Sri Lanka and no telephone number), is using excessive queries (~ >500M queries per day on a "free dns" domain) and attracting repeated, multiple DDoS attacks.
As such, we will be wildcarding this zone and setting a long TTL fairly soon.
If you're actually using this RBL in your MTAs, now's a good time to stop. (this RBL is broken on 5 out of it's 6 delegated nameservers across 3 separate providers).