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.
I think the fake trading volume is difficult to check and any exchanges are using this to get high rankings at CMC. As far as I know in November there will be very special information and will certainly eliminate the fake trading volume at some exchanges. I hope this can go smoothly because a lot of bad exchanges like Latoken, P2P, Vindax always have very high ratings in this market.
Currently, I only trust the top exchanges that are chosen by people because these are exchanges with large trading volumes and can liquid at any time if you want.