The folks at http://getipintel.net/ http://getipintel.net/ can give you some decent information about wether an IP looks spammy or not. > Given an IP address,

The folks at http://getipintel.net/ http://getipintel.net/ can give you some decent information about wether an IP looks spammy or not. > Given an IP address, the system will return a probabilistic value (between a value of 0 and 1) of how likely the IP is a VPN / proxy / hosting / bad IP. A value of 1 means that IP is explicitly banned (a web host, VPN, or TOR node) by our dynamic lists. We've been using it for a while and are pretty happy.