If you are using OpenDNS and get DNS timeouts for the uribl.com Blacklist (UB-BLACK), that is because the administrators of URIBL decided to reject DNS requests from OpenDNS. The reason is that OpenDNS servers are alone responsible for 50 million DNS requests per day on the public mirrors of uribl.com. We recommend that you use your own DNS servers for ORF or if you are doing lookups in large volume (in case of uribl.com, 300.000 requests per day), set up a data feed. Alternatively, you can try getting OpenDNS to set up a data feed themselves.
Using your ISP DNS servers as DNS forwarders could also trigger a similar response from DNSBL/SURBL operators, because your lookups and everyone else’s on your ISP’s network add up.
For large volume lookups, please consider that the vast majority DNS blacklists and SURBLs are non-profit and run on donated hardware and bandwidth. Before using these, make sure to check their fair use policy and set up a data feed if necessary.