you are correct this is a scam to scare you into paying a fee to a collector who is not authorized by anyone to collect any debt. You would have received multiple documents mailed to your residents showing the account history all the transactions and any balances owed before any court action could be taken to collect any debt.
The debt collection agency would have attempted to contact you by phone multiple times to resolve the debt and collect a payment from you in person by credit card over the phone. Email is the very "last method" of contact because it is considered a "last ditch effort", so "don't even bother with these idiots" they are more shady than an Oak tree.
just click on the little button marked "delete", and have a lovely day ..... :-)
I liked: Check cashing services.
I didn't like: Scam emails.