Another useful site for this is DNSSTUFF. For example (this is an
IP that IS blacklisted):
http://www.dnsstuff.com/tools/ip4r.ch?ip=211.158.13.154
The nice thing about this site is that it checks multiple RBLs.
The test should be set up under Advanced to verify that the
return string DOES NOT CONTAIN:
"innerHTML += 'LISTED"
I've checked the "Case sensitive' box but I'm not sure that's
really necessary.
Also, because this check can take a while to complete, I've set my
timeout on this test to 45 seconds.
Finally, be kind to the remote site - a test interval of once a day should be sufficient.