Exact same message, copied and pasted because it came back within seconds. Tell your friends to use common sense, people that take two month honeymoons don't buy used sporting goods nor do they offer an odd number like $70 to hold it. If it sounds too good to be true, IT IS!
Don't cash the check. Take it, the envelope and any instructions to the post office and turn it all in as postal fraud. Alternatively take it all to your bank, ask to speak to someone who handles potential fraud and see if they can investigate.
I'm selling something on craigslist and I got the same story (text) as the others. Offered the extra $70. I said I would not hold it, he asked for my info so his secretary could send cashiers check and arrange pick up. I told him to give me secretaries contact info and I prefer a cash transaction. Haven't heard any more from him.