I don't know if CMC does the volume checking. It's funny because some of top on the list of cryptocurrency exchanges are unknown or not really popular. I think CMC are just after the money. They should have top exchanges with fake volumes too. Better make a poll here and see what exchange give them a better experience. I don't trust CMC. So better do something to make things clear what exchange is suitable for you. Making a poll here is a good way to start.