mjb:  the other Community member, carol, is correct  This is "the classic" of all scams. It's so "old" that it's "tired"...but there are still people who are new to being rental owners and they have not seen this yet.  But, believe us...it is a scam.  Forget about the check they send to you...it's a fake.l...don't even try to cash it.  Just tear it up.  You do not have a reservation...it was never intended that anyone  would check into your place.  So, just to be "thorough" do as  Carol said:  email them to say that someone came along and booked the place already. Don't let them try to book another date.  Just stop responding.

Don't even bother lying and telling them that somebody else has rented your place.  This is the granddaddy of scams that originated in Nigeria.  Tell them that you are aware of their scam and all of their information has been forwarded to the authorities.  Or...you could play with them a bit.  Tell them to send their payment in cash (small bills preferred) because you could really use the money.  If they happen to make a mistake and send far more than you requested, you will be certain to refund the difference asap....as soon as you return from shopping.

Ah, play with them if you want.  They aren't interested in seeking revenge.  They're sitting in an internet cafe somewhere in Nigeria or the Ukraine looking to hook one of the 0.01% of vacation owners who might fall for their scam.  I've taken both routes and most likely you'll never hear from them again.

Just tell them you don't rent to people that are grammatically challenged.