Baddomain.com
michael - This domain was originally acquired to prove a minor point -- specifically, that any domain that can be registered is perfectly valid as far as the Internet is concerned, even though a human observer may not consider it so. To a computer, "No Name" is, and should be, a valid person's name, as is "n/a" and "Unknown" -- semantically, they're all just names, and indistinguishable from a "real" looking name. To put the time in context, this was before spam was considered a problem, and when companies didn't routinely market or sell through the Internet -- for example, the company I worked for, a billion-dollar, 3,000-employee company, didn't have a domain name of its own.
Since then, it's become routine for companies to ask for email addresses to view content or download, and become routine for people not particularly interested in receiving more email from those companies to type in random email addresses -- often the address "baduser@baddomain.com" which, as you might expect, is handled by our mail servers here. This was once a valid address, and I collected, filtered, and arranged everything that came in. From a time where about 10% of the mail was interesting, on the day I turned off the email address, there was nothing but common spam for pump-and-dump investments, Nigerian scams, account phishing, mortgage offers, viruses, casinos, dubious medication -- in short, a cross section of the annoying junk people get every day, but nothing of actual interest or value.
Subsequent to establishing this domain, it has been used as an example in configurations of mailers and spam filters, which in and of itself is not so bad, except for the inevitable doofus who takes the example quite literally and either sends us huge volumes of mail while testing their setup (usually with some bafflement that the mail is bouncing and not simply failing to find a DNS record) or, even more irritatingly, banning the domain or adding it to filters because of its name.
So, if you're wondering if this domain is legitimate, it most certainly is, just like any other domain, or like a person whose name is legally changed to "Not Applicable." If you're looking for disposable addresses, please don't use this one. The correct domain to use is example.com, which is the only one set aside for this purpose.