Lisa Muir writes:
I've been adding dns blacklists through the courier webadmin with great results. Wanted to add lashback to the list, and found this in their info:if you wish to check whether 192.168.1.100 is listed in the UBL, you would perform a DNS lookup on 100.1.168.192.ubl.unsubscore.com Is this how the web configured DNS blacklists work or do they simply
They all work this way.
make a reverse DNS lookup on the IP address? I was hoping to migrate the blacklist lookups to a localhost BIND and effectly use it as a proxy for courier to make one single rdns lookup on, but if they all operate like lashback, then thats not going to work with multiple dnsbl's
Why not? It'll work just fine. Of course, it will get slow. Once you get beyond 3-4 DNSBLs, the server will spend a noticeable amount of time waiting for remote DNS queries to come back.
The usual solution is to make arrangements with your DNSBL's operators to let your nameservers do zone transfers, rather than ad-hoc queries. This will effectively keep your DNS lookups local, and each check essentially translates to a rather fast database dip. You can't expect it to get faster than that.
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