tropicalnames.com is the new name for the pedma.com domain appraisal scam. The basic pitch is that you get an unsolicited offer for a domain name, along with a list of recognised appraisal companies. The cheapest company is controlled by the scammers who sent the email (apparently operating out of Canada).
Domain was registered on 3rd April 2008 with anonymised details and is hosted on 126.96.36.199 in Malaysia. If you get one of these, treat it as spam and file a complaint with abuse -at- piradius.net.