It does SMTP requests, trying to send mail (and aborting) to check the emails. It first tries a bogus gqjcqjcbhkjxcg@thedomain.com to see if the server throw an error (and was not config as a catchall), then for Bill Gates, tries : - billgates@ - gatesbill@ - bgates@ - gatesb@ - bill@ ... - bill.gates@ ...

but they don't try bg@thedomain.com

The results also depends of the order of the tests. If you have bill@ that redirects to bill.gates@, as they try bill@ before bill.gates@, it will tell you that bill@ is the address.

Clever, but used by spammers and list makers for years (those who scan whois domain infos and reconstruct the email with your name and the domain).

Was wondering the same thing. Even tried finding a blog, but looks like it's a pre-drop domain from a previous venture (http://mashable.com/2008/02/01/gimado/)