Some domain name related scams are easy to sniff out because if you do a Google search on their name, you find hundreds of pages showing examples of it with warnings to not send them money. This one is one of those.
The folks behind Domain Listings send you a letter by snail mail (to give it more weight and importance) telling you an amount is due by a deadline to avoid "expiration". In this case, expiration of something you didn't have to begin with, but scary words make people send checks faster.
Here's the front and back of a recent letter we received from these scammers (click to view larger size):
Over the years I've seen their wording change a bit, where they now include phrases like "This is not a bill. This is a solicitation. You are under no obligation to pay the amount stated above unless you accept this offer." I'm pretty sure they've done this to avoid crackdowns from law enforcement. Their whole business model is worrying people who are unsure how domain or website services work into sending money without questioning. Always read the fine print! (After reading that, if you're still unsure, get in touch and ask about it - we'll be happy to help!)