How do I tell if a check I received from craigslist is a fraud?

I was selling a wedding gown on craigslist. A gentleman asked several questions seeming really interested, then asked if I would ship the dress. I agreed to do so. A couple of days later he wrote and said that he had sent a check for more, wanting me to send the rest to his daughter with the dress as her wedding present. I umed at that moment it was a scam, but now I'm confused. He sent the check and I called the issuing bank to find that it is a real open and active account and the signature is from a signer on the account. They wouldn't verify the funds as I was not on the account though. Is there something else I should do to verify the check, or does that mean that it's good? I just don't want to cash the check just to find out later that it was a fake, but don't want to miss out on the money if it is real.