This is one of the most common lately. But I think not all scam. Because sometimes there may be some delays for certain reasons.
As a response to your question, I can not give a clear reply, but as experience increases, you are more alert.
not all fraud and not all bad, so there are still opportunities for us if we want to try to look carefully.
everything here is at risk and we must be able to take risks so we must be vigilant and you must be prepared in any situation.