>>jgraha+(OP)
I would never use Cloudflare. They hide spammers and refuse to do anything about them. The same mass spammer will register site after site for months, sending snowshoe spam, and cloudflare refuses to do anything. At one point this was taking up about 80% of our incoming spam, and most of it was getting through spam filters due to the snowshoeing. You could see the same registration info for hundreds of domains over months, all sending spam, but cloudflare doesn't give a shit.
The only solution I found was to put a 15 minute delay on all incoming email from a cloudflare domain, then do a second check of the blacklists. This solved the problem, as the sending ips (not cloudflare) tended to get blacklisted within 15 minutes.
In my mind if you're hiding people's websites behind your "cloud", you have a responsibility to kick off the spammers.