Read this ... carefully!
http://www.fdic.gov/consumers/consumer/news/cnwin0607/scams.html
Extract:
"In these cases, the depositor most likely will be held responsible for the entire amount of the fraudulent check."
Instead of cashing the check, or sending it back, take it and the envelope in which it came to the post office. They will use it as evidence and pursue the scammer.
Gentleman wanted to confirm whether a specific accounting manager still works for the company. I was in the middle of stating that employee information cannot be provided over the phone and must be requested in writing when he hung up.