These are websites that allow you to either check a single IP to see if it’s on any of a number of blocklists or check an range of IP addresses.
This can be very useful and I recommend trying all the ones I have listed and use what you like. I like and recommend all of these. Each has there benefits and it’s not unusual to be using more than one.
multirbl
URL: http://multirbl.valli.org/lookup/
Notes: Very thorough lookup for a single IP or domain name. I can’t imagine there is an RBL this doesn’t check.
MXToolBox
URL: https://mxtoolbox.com/blacklists.aspx
Notes: Lookup for a single IP or domain against common blocklists. This one is pretty fast.
The Anti-Abuse Project – RBLMON
URL: http://www.anti-abuse.org/projects/rblmon/
Notes: Lookup for a single IP or domain against common blocklists. They have a monitoring service which I’ve never used.